electronics & communication engineering part ii · 2018. 6. 1. · analog electronics section 1...

Contents

AnalogElectronics

Section 1 : Oscillators, Amplifier ......................................................................................................... 5

Section 2 : Transistor, Stabilizer ........................................................................................................ 18

Section 3 : BJT amplifier, Zener ......................................................................................................... 29

Section 4 : Frequency, Diode ............................................................................................................ 39

Section 5 : Impedance, Amplifier ...................................................................................................... 50

Section 6 : Capacitor, Rectifier .......................................................................................................... 61

Section 7 : FET, Wien bridge ............................................................................................................. 74

Section 8 : Crystal Oscillator, Resistance .......................................................................................... 84

Section 9 : Coupling........................................................................................................................... 92

Section 10 : CE amplifier, JEFT ........................................................................................................ 100

Section 11 : Hartley Oscillator, Amplifier gain ................................................................................ 108

Section 12 : Aperture circuit, Clipper .............................................................................................. 117

Section 13 : Ripple Factor, Delay Equlazier ..................................................................................... 127

Section 14 : TRIAC, Power Ampliflier .............................................................................................. 136

Section 15 : CMOS, Darlington Pair ................................................................................................. 145

Section 16 : Coupling Capacitor ...................................................................................................... 155

Section 17 : Rectifier Circuits, Impedance ...................................................................................... 164

Section 18 : DEMOSFET, Swamped Amplifier ................................................................................. 173

Section 19 : Open Loop Configuration ............................................................................................ 182

3

Analog Electronics

Section1:Oscillators,Amplifier

1. A half wave diode rectifier has a capacitance input filter. If input voltage is Vm sin ωt, PIV is

A. Vm B. 2 Vm C. 3 Vm D. 4 Vm

2. The 'h' parameters of the circuit shown in the figure are hib = 25 ω, hfb = 0.999 and hob= 10-6ω The Voltage gain is

A. 0.99 B. 1.98 C. 2.0 D. 4

3. The load impedance ZL of a CE amplifier has R and L in series. The phase difference between output and input will be

A. 180° B. 0 C. more than 90° but less than 180° D. more than 180° but less than 270°

4. In the op-amp circuit of figure, V0 =

A. Vi B. 3 Vi C. 5 Vi D. 0.5 Vi

5

5. Si transistor of following figure has a = 0.9 and ICE= 0, VEE = 5 V and VCC = 13 V, then RE will be if IEQ = 1 mA

A. 3 kω B. 4 kω C. 5 kω D. 4.3 kω

6. Assertion (A): For large signal variations an amplifier circuit has to be analysed graphically

Reason (R): The output characteristics of a transistor is nonlinear.

A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

7. DC amplifiers have a tendency to be unstable.

A. True B. False

8. In figure, VEB = 0.6 V, β = 99. Then VC and IC are

A. 9.3 V and 1.98 mA respectively B. 4.6 V and 1.98 mA respectively C. 9.3 V and 0.02 mA respectively D. 4.6 V and 0.02 mA respectively

6

9. In figure The minimum and maximum load currents are

A. 0 and 60 mA B. 0 and 120 mA C. 10 mA and 60 mA D. 10 mA and 120 mA

10. The quiescent collector current IC, and collector to emitter voltage VCE in a CE connection are the values when

A. ac signal is zero B. ac signal is low C. ac signal is negative D. either (a) or (b)

11. In figure VCC = 20 V and R = 10 kω. If VBE = 0.7 V, I1 =

A. 1.93 mA B. 19.3 mA C. 0.193 mA D. 193 mA

12. In figure ID = 4 mA. Then VS =

A. 20 V B. 4.4 V C. 0.4 V D. 0.44 V

7

13. The efficiency of a full wave rectifier using centre tapped transformer is twice that in full wave bridge rectifier.

A. True B. False

14. A half wave diode circuit using ideal diode has an input voltage 20 sin ωt volts. Then average and rms values of output voltage are

A. and 10 V

B. and 10 V

C. and 5 V

D. and 5 V

15. Study the circuit of figure and examine the following statements

It is an active low pass finer. It is a second order filter. The change in gain is 40 dB/decade. Which of the above statements are correct?

A. 1, 2 and 3 B. 1 and 2 C. 1 and 3 D. 2 and 3

16. Which power amplifier can deliver maximum load power?

A. Class A B. Class AB C. Class B D. Class C

8

17. An amplifier with loop gain Aβ will be more stable for value of Aβ as

A. 0.95 B. 0.7 C. 1.2 D. 1.5

18. Figure shows the self bias circuit for CE amplifier and its equivalent circuit. VBB and RB respectively are

A. 10 V and 4 k ohm B. 5 V and 4 k ohm C. 2 V and 4 k ohm D. 2 V and 10 k ohm

19. For a system to work, as oscillatorillator the total phase shift of the loop gain must be equal to

A. 90° B. 45° C. 270° D. 360°

20. In a BJT circuit a pnp transistor is replaced by npn transistor. To analyse the new circuit

A. all calculations done earlier have to be repeated B. replace all calculated voltages by reverse values C. replace all calculated currents by reverse values D. replace all calculated voltages and currents by reverse values

21. Negative feedback reduces noise originating at the amplifier input.

A. True B. False

9

22. In a circuit of figure, Vs = 10 cos(ωt) power drawn by the 2ω resistor is 4 watts. The power factor is

A. 0.3 B. 0.4 C. 0.6 D. none

23. To prevent a DC return between source and load, it is necessary to use

A. resistor between source and load B. inductor between source and load C. capacitor between source and load D. either (a) or (b)

24. Which of the following oscillators is suitable for frequencies in the range of mega hertz?

A. RC phase shift B. Wien bridge C. Hartley D. Both (a) and (c)

25. The output V0 in figure is

A. -100 V B. -100 mV C. 10 V D. 10 mV

10

26. A bridge rectifier circuit has input of 50 Hz frequency. The load resistance is RL and filter capacitance is C. For good output wave shape, the time constant RLC should be at least equal to

A. 10 ms B. 20 ms C. 50 ms D. 100 ms

27. An RC coupled amplifier has an open loop gain of 200 and a lower cutoff frequency of 50 Hz. If negative feedback with β = 0.1 is used, the lower cut off frequency will be

A. about 50 Hz B. about 5 Hz C. about 2.38 Hz D. about 70.5 Hz

28. The transistor of following figure in Si diode with a base current of 40 μA and ICBO = 0, if VBB = 6V, RE = 2 kω and β = 90, IBQ = 20 μA then RB =

A. 200 kω B. 265 kω C. 150 kω D. 100 kω

29. In class C operation of an amplifier circuit, the collector current exists for

A. 360° of input wave B. 180° of input wave C. more than 180° of input wave D. less than 180° of input wave

11

30. Figure is a 24 Vr stabilized power supply. The zener is 24 V, 600 mW. The minimum zener current is 10 mA. Proper values R and maximum load current are

A. 320 ω, 10 mA B. 400 ω, 15 mA C. 400 ω, 10 mA D. 320 ω, 15 mA

31. The input impedance of op-amp circuit of figure is

A. 120 k ohm B. 110 k ohm C. infinity D. 10 k ohm

32. The self bias provides

A. stable Q point B. large voltage gain C. high input impedance D. high base current

12

33. In figure v1 = 8 V and v2 = 8 V. Which diode will conduct?

A. D1 only B. D2 only C. Both D1 and D2 D. Neither D1 nor D2

34. In the amplifier circuit of figure hfe = 100 and hie = 1000 ω. The voltage gain of amplifier is about

A. 0.33 B. 0.5 C. 0.66 D. 1

35. An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly a

A. sine wave B. square wave C. triangular wave D. (a) or (c)

13

36. Gain of the amplifier is 'A'. Then the I/P impedance and O/P impedance of the closed loop amplifier shown below would be

A.

B.

C.

D.

37. In figure what is value of IC if βdc = 100. Neglect VBE

A. 5 mA B. 5 μA C. 10 mA D. 10 μA

38. Assertion (A): CE amplifier is the most widely used BJT amplifier

Reason (R): CE amplifier has zero phase difference between input and output


14

39. In figure what is the base current if VBE = 0.7 V

A. 10 mA B. 9.3 mA C. 10 μA D. 9.3 μA

40. Consider the following statements : A clamper circuit

adds or subtracts a dc voltage to a waveform does not change the waveform amplifiers the waveform Which are correct? A. 1, 2 B. 1, 3 C. 1, 2, 3 D. 2, 3

41. Gain of the amplifier is 'A'. Then the I/P impedance and O/P impedance of the closed loop amplifier shown below would be

A.

B.

C.

D.

15

42. If the input to the ideal comparator shown in the figure is a sinusoidal signal of 8 V (peak to peak) without any DC component, then the output of the comparator has a duty cycle of

A. 1/2 B. 1/3 C. 1/6 D. 1/12

43. Maximum efficiency of class B power amplifier is 50%.

A. True B. False

44. For a base current of 10 μA, what is the value of collector current in common emitter if βdc = 100

A. 10 μA B. 100 μA C. 1 mA D. 10 mA

45. If an amplifier with gain of - 1000 and feedback factor β = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would be

A. 10% B. 5% C. 0.2% D. 0.01%

46. In figure the saturation collector current is

A.

B.

C. D. none of the above

16

47. To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to use

A. surge resistor B. surge inductor C. surge capacitor D. both (a) and (b)

48. In figure v1 = 8 V and v2 = 4 V. Which diode will conduct?


49. A CB amplifier has re = 6 ω, RL = 600 ω and a = 0.98. The voltage gain is

A. 100 B. 600 x 0.98 C. 98 D. 6

50. A forward voltage of 9 V is applied to a diode in series with a 1 kω load resistor. The voltage across load resistor is zero. It indicates that

A. diode is short circuited B. diode is open circuited C. resistor is open circuited D. diode is either short circuited or open circuited

Answer of Analog digital : Oscillatorliallators, Amplifier

1‐>2 , 2‐>4 , 3‐>4 , 4‐>3 , 5‐>4 , 6‐>1 , 7‐>1 , 8‐>1 , 9‐>2 , 10‐>1 , 11‐>1 , 12‐>2 , 13‐>2 ,

14‐>2 , 15‐>1 , 16‐>4 , 17‐>2 , 18‐>3 , 19‐>4 , 20‐>4 , 21‐>2 , 22‐>3 , 23‐>3 , 24‐>3 , 25‐>2

, 26‐>4 , 27‐>3 , 28‐>2 , 29‐>4 , 30‐>4 , 31‐>4 , 32‐>1 , 33‐>3 , 34‐>4 , 35‐>2 , 36‐>2 , 37‐

>3 , 38‐>3 , 39‐>4 , 40‐>1 , 41‐>2 , 42‐>2 , 43‐>2 , 44‐>3 , 45‐>3 , 46‐>3 , 47‐>1 , 48‐>2 ,

49‐>3 , 50‐>2

17

Analog Electronics

Section2:Transistor,Stabilizer1. In figure as the load resistance is changed

A. the zener current remain constant B. the load current remains constant C. the output voltage remains constant D. the output voltage and current through R remain constant

2. In figure if C is replaced by short circuit then RB will be

A. 425 K B. 412 K C. 474 K D. 400 K

3. For high frequencies a capacitor like

A. an open circuit B. a short circuit C. either open circuit or short circuit D. none of the above

18

4. In following figure, what will be R1 and R2 for maximum symmetrical swing if VCSat ≈ 0. Given that RE = 200 ω, RC = 400 ω, VCC = 20 V, β = 99

A. 6 k B. 3 k, 6 k C. 9.9 k, 2.4 k D. 2.4 k, 9.9 k

5. The ripple factor of a half wave rectifier is more than 2.

A. True B. False

6 The open loop gain of an amplifier is 200. If negative feedback with β = 0.2 is used, the closed loop gain will be

A. 200 B. 40.12 C. 4.878 D. 2.2

7. The input voltage for starting oscillations in an oscillator is caused by

A. negative feedback B. positive feedback C. noise voltage in resistors D. a special generator

19

8. For CE amplifier of figure, the slope of ac load line is

A.

B.

C.

D.

9. In figure the dc emitter current of each transistor is about

A. 4 mA B. 2 mA C. 3 mA D. 1 mA

20

10. Assertion (A): The circuit in figure produces repetitive narrow pulses when input is fed with sine or triangular waveform having peak value more than + V Reason (R): The high gain op-amp produces voltages at two levels. If input is more than + V, the output is + 15 V otherwise the output is - 15 V.


11. The current flowing in a certain P-N junction at room temperature is 2 x 10-7 Amp. When a large reverse biased voltage is applied. Calculate the current flowing when 0.1 volts is applied.

A. 9 μA B. 10 μA C. 2 μA D. 4 μA

12. The value of parameter re used in re transistor model

A. increases with increase in temperature B. decreases with increase in temperature C. is not affected by increase in temperature D. either (b) or (c)

13. An RC oscillator uses

A. one RC combination B. two RC combinations C. at least three RC combinations D. either (a) or (b)

14. In a push pull circuit

A. each transistor conducts for 180° B. each transistor conducts for more than 180° but less than 360° C. each transistor conducts for less than 180° D. the period of conduction of each transistor depends on circuit configuration

15. In a bridge rectifier circuit the rms value of input ac voltage is 10 V. The PIV across each diode is

A. 7.07 V B. 14.14 V C. 10 V D. 28.28 V

21

16. Feedback factor may be less or more than 1.

A. True B. False

17. An op-amp has zero gain for common mode inputs. Then CMRR =

A. zero B. infinite C. high D. low

18. The ideal characteristics of a stabilizer is

A. constant output voltage with low internal resistance B. constant output current with low internal resistance C. constant output voltage with high internal resistance D. constant internal resistance and constant output current

19. A transistor with a = 0.9 and ICBO = 10 μA is biased so that IBQ = 90 μA. Then IEQ will be

A. 5.15 mA B. 5.2 mA C. 5 mA D. 990 mA

20. Assertion (A): Negative feedback reduces the bandwidth of an amplifier

Reason (R): Negative feedback stabilizes the gain of an amplifier


21. In following figure find VDSQ by assuming gate current is negligible for the p-channel JFET. (if IDQ = - 6 mA, RS = 0, VDD = -18 V, RD = 2 kω, IDSS = - 10 mA, IPO = - 3 V)

A. 4 V B. - 6 V C. - 10 V D. 6 V

22. The dissipation at the collector is in the quiescent state and increases with excitation in the case of a

A. class A series fed Amplifier B. class A transistor coupled Amplifier C. class AB amplifier D. class B amplifier

22

23. In figure, transistor βdc = 100 and LED voltage when it is conducting is 2 V. Then the base current which saturates the transistor is

A. 18 mA B. 1.8 mA C. 0.18 mA D. 0.018 mA

24. An ideal op-amp has zero slew rate.

A. True B. False

25. In the diode circuit of figure the diodes are ideal. The average current through ammeter is

A.

B.

C.

D.

26. The main advantage of CMOS circuit is

A. high gain B. high output impedance C. low power consumption D. high gain and high output impedance

23

27. Assertion (A): In a full wave rectifier output the lowest ac component is at twice the input frequency

Reason (R): In a full wave rectifier, the output waveform consists of half sinusoids


28. A full wave rectifier using centre tapped transformer and a bridge rectifier use similar diodes and have equal no load output voltage. Under equal load conditions

A. Output voltage of bridge rectifier B. Output voltage of bridge rectifier will be more than that of other C. Output voltage of both will be exactly equal D. Output voltage of any one may be more than that of other

29. Assume that op-amp in figure is ideal. If input Vi is triangular, the output V0 will be

A. square wave B. sine wave C. triangular wave D. parabolic wave

30. Find resistance RB to bring transistor to threshold of saturation VCB = 0, VBE = 0.7 V,= 0.96

A. 1.5 kω B. 15 kω C. 10 kω D. 1 kω

24

31. A transistor has two p-n junctions. The batteries should be connected such that

A. both junctions are forward biased B. both junctions are reverse biased C. one junction is forward biased and the other is reverse biased D. either (a) or (b)

32. The coupling capacitor in amplifier circuits

A. affects dc biasing B. does not affect dc biasing C. affects dc biasing to some extent D. both (a) and (c)

33. In a class C power amplifier the input signal has a frequency of 250 kHz. If the collector current pulses are 0.1 μs wide, the duty cycle of current waveform is

A. 50% B. 25% C. 2.5% D. 0.25%

34. The open loop gain of an ideal op-amp is

A. infinite B. very high C. neither high nor low D. low

35. A non-inverting op-amp summer is shown in figure, the output voltage V0 is

A.

B. 3 sin (100t) C. sin (100t) D. 2 sin (100t)

36. In an amplifier the voltage gain is the ratio of

A. output voltage and emitter resistance B. output voltage and input current C. output voltage and input voltage D. none of the above

25

37. In figure, voltage across R2 = + 10 V. If VBE = 0.7 V and VE = 0.7 V and RE = 10 kω, current through RE is

A. 1 mA B. 0.93 mA C. 2 mA D. 1.86 mA

38. Ac signals are given to both inverting and non-inverting terminals of an op-amp. When will the output maximum

A. when the phase difference between the inputs is 0° B. when the phase difference between the inputs in 90° C. when the phase difference between the inputs is 180° D. when the phase difference between the inputs is 0 or 180°

39. In a half wave diode rectifier circuit the current flows in the load circuit for

A. 90° in each cycle B. 180° in each cycle C. 270° in each cycle D. 360° in each cycle

40. In an amplifier with a gain of - 1000 and feedback factor β = - 0.1, the change in gain is 20% due to temperature. The change in gain for feedback amplifier will be

A. 10% B. 5% C. 0.2% D. 0.01%

26

41. In following circuit, RB will be if VCC = 10 V, VS = 2 V, RC = 5 kω, RS = 90 kω, β = 50, ICE= 0, VCEsat = 0.1 V

A. 230 K B. 235 K C. 240 K D. 250 K

42. The critical frequency of the circuit of figure is

A.

B.

C.

D.

43. A typical value of gm for a FET is about 25 μs.

A. True B. False

44. Which of the following power amplifiers has highest efficiency?

A. Class A B. Class AB C. Class B D. Class C

27

45. In following figure find VGG by assuming gate current is negligible for the p-channel JFET. (if IDQ = - 6 mA, RS = 0, VDD = -18 V, RD = 2 kω, IDSS = - 10 mA, IPO = - 3 V)

A. 0.67 V B. 6.7 V C. 7 V D. 0.3 V

46. A 12 kHz pulse wave-form is amplified by a circuit having an Upper cut-off frequency of 1 MHz. The minimum input pulse width that can be accurately reproduced is

A. 83.33 μ sec B. 1 μ sec C. 0.1 m sec D. 3.5 m sec

47. A full wave rectifier circuit using centre tapped transformer and a bridge rectifier are fed at 100 V, 50 Hz. The frequencies of outputs in these two rectifiers are

A. 100 Hz each B. 50 Hz each C. 100 Hz and 50 Hz D. 50 Hz and 100 Hz

48. A difference amplifier using op-amp has closed loop gain = 50. If input is 2 V to each of inverting and non-inverting terminals, output is 5 mA. Then CMRR =

A. 20000 B. 2000 C. 200 D. 20

49. In a CE amplifier drives a low load resistance directly the result will be

A. overloading of amplifier B. underloading of amplifier C. overloading or underloading of amplifier depending on circuit D. none of the above

50. When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is

A. zero B. constant C. alternating D. distorted

Answer of Analog digital : Transistor, Stabilizer

1‐>4 , 2‐>3 , 3‐>2 , 4‐>4 , 5‐>2 , 6‐>3 , 7‐>3 , 8‐>1 , 9‐>4 , 10‐>1 , 11‐>1 , 12‐>1 , 13‐>3 ,

14‐>1 , 15‐>2 , 16‐>2 , 17‐>2 , 18‐>1 , 19‐>4 , 20‐>4 , 21‐>2 , 22‐>4 , 23‐>3 , 24‐>2 , 25‐>2

, 26‐>3 , 27‐>2 , 28‐>1 , 29‐>1 , 30‐>1 , 31‐>3 , 32‐>2 , 33‐>3 , 34‐>1 , 35‐>1 , 36‐>3 , 37‐

>2 , 38‐>3 , 39‐>2 , 40‐>3 , 41‐>2 , 42‐>2 , 43‐>2 , 44‐>4 , 45‐>1 , 46‐>2 , 47‐>1 , 48‐>1 ,

49‐>1 , 50‐>4

28

Analog Electronics

Section3:BJTamplifier,Zener

1. An oscillator requires an amplifier

A. with negative feedback B. with positive feedback C. with either positive or negative feedback D. none of the above

2. In full wave rectification, if the input frequency is 50 Hz, then frequency at the output of filter is

A. 50 Hz B. 0 Hz C. 100 Hz D. 75 Hz

3. In the circuit of figure the diode

A. will conduct as the whole cycle B. will conduct in the positive half cycle C. will not conduct D. will conduct from 30° to 150° in the positive half cycle

4. If the Q of a single stage single tuned amplifier is doubled, the bandwidth will

A. remain the same B. become half C. become double D. become four times

5. For a BJT if β = 50, ICEO = 3 μA and IC = 1.2 mA then IB

A. 24 μA B. 23 μA C. 20 μA D. 10 μA

6. A transistor has a power rating of 8 W for a case temperature of 25°C. If derating factor is 30 mW/°C, the power rating for 55°C, case temperature is

A. 8 W B. 7.5 W C. 7.1 W D. 6.8 W

29

7. In figure, ID = 4 mA. Then VD =

A. 20 V B. 10 V C. 30 V D. 1 V

8. Assertion (A): In CE amplifier the emitter is at ground potential for ac signals

Reason (R): A CE amplifier has near unity voltage gain


9. In figure the zener current

A. is always 130 mA B. may vary between 10 mA and 130 mA C. may vary between 60 mA and 130 mA D. is always equal to 65 mA

30

10. Figure shows a portion of linear v - i characteristics of diode. If applied voltage is + 6 V, the current will be

A. 42 mA B. 48 mA C. 51 mA D. 54 mA

11. A circuit using an op-amp is shown in the given figure. It has

A. voltage series feedback B. voltage shunt feedback C. current shunt feedback D. current series feedback

12. In a CE amplifier

A. both ac and dc load lines have the same slope B. the ac load line has more slope than dc load line C. the ac load line has less slope than dc load line D. the two load lines may have slope more than the other

13. An integrating amplifier has resistance in feedback path.

A. True B. False

14. A full wave bridge diode rectifier uses diodes having forward resistance of 50 ohms each. The load resistance is also 50 ohms. The voltage regulations is

A. 20% B. 50% C. 100% D. 200%

31

15. The dc load current in a bridge rectifier circuit is 10 mA. The dc load current through each diode is

A. 40 mA B. 20 mA C. 10 mA D. 5 mA

16. In the CE equivalent circuit of figure, the voltage gain is

A. 200 B. 40 C. 5 D. 1000

17. Calculate the conductivity of pure silicon at room temperature when the concentration of carriers is 1.6 x 1010 per cm3. Take μe = 1500 cm2/V-sec, μh = 500 cm2/V-sec at room temperature,

A. 5.12 x 10-16 B. 5 x 10+16 C. 1016 D. 5 x 1020

18 In a two stage CE amplifier circuit, the ac collector resistance of the first stage depends on

A. load resistance B. input impedance of first stage C. input impedance of second stage D. all of the above

19. When load is coupled to class A amplifier through transformer, efficiency decreases.

A. True B. False

20. For dc the current through coupling capacitor in CE amplifier circuit is

A. very high B. high C. low D. zero

32

21. In the circuit shown in figure, RC = 10k, RE = 150ω, β = 100, I = 1 mA. The value will be

A. 50 B. 100 C. 192 D. 400

22. A P-channel MOSFET operating in the enhancement mode is characterized by Vt = - 4 V and IDQ = - 10 mA, when VGSQ = - 5.5 V, what will be VGSQ if IDQ = -15 mA and ID, on = - 16 mA

A. - 2 V B. 3 V C. 0.13 V D. 1.3 V

23. In a CE amplifier the collector resistance is short circuited. The ac output voltage will

A. increases B. remains the same C. increases or decreases D. decreases

24. A power transistor dissipates 5 W. If ambient temperature is 30° and case to air thermal resistance is 10° C/W, the case temperature is

A. 80°C B. 20°C C. 32°C D. 305°C

25. In a transistor CE mode, VCC = +30 V. If the transistor is in cut off region, VCE =

A. +30 V B. +20 V C. 10 V D. zero

26. In a commercially available good power supply the voltage regulation is about

A. 1% B. 5% C. 10% D. 20%

33

27. The gain of an FET amplifier can be changed by changing

A. rm B. gm C. Rd D. none of the above

28. The most commonly used bias in BJT amplifier circuits is

A. voltage divider bias B. emitter bias C. collector bias D. collector feedback bias

29. In figure VBE = 0.7 V. The base current is

A. above 97 μA B. about 97 mA C. about 75 μA D. about 75 mA

30. An ideal power supply has

A. zero internal resistance B. very high internal resistance C. high output resistance D. both (b) and (c)

31. The open loop gain of an actual op-amp is about 100.

A. True B. False

32. Two CE stages, 1 and 2 are coupled through a capacitor. VCC is the same for both. Base resistances RB1 and RB2 are such that RB1 > RB2. Then

A. base currents for both stages are equal B. base current of stage 1 is more than that of stage 2 C. base current of stage 2 is more than that of stage 1 D. either (b) or (c)

34

33. In the circuit figure LED will be on when v1 is

A. less than 6 V B. more than 6 V C. less than 12 V D. more than 12 V

34. The inverting op-amp shown in the figure has an open loop gain to 100. The closed loop Is

A. -8 B. -9 C. -10 D. -11

35

35. Which of the following?

A. Voltage series feedback and decrease I/P impedance. B. Voltage shunt feedback and decrease I/P impedance. C. Voltage series feedback and increase I/P impedance. D. Voltage shunt feedback and increase I/P impedance.

36. Figure shows a self bias circuit for FET amplifier, ID = 4 mA. Then IS =

A. 4 mA B. 2 mA C. 0.4 mA D. 0.2 mA

37. Positive feedback is mainly used in

A. oscillators B. thyristors C. voltage regulators D. both (a) and (b)

38. The units of transistor h parameters h11 and h22 are the same.

A. True B. False

36

39. In a transistor E mode the collector current with the transistor in cut off region is

A. zero B. high C. equal to saturated value D. none of the above

40. The parameter h11 for CB circuit is higher than that for CE circuit.

A. True B. False

41. An R-C coupled amplifier has mid-frequency gain of 200 and a frequency response from 100 Hz to 20 kHz. A negative feedback network with β = 0.2 is incorporated into the amplifier circuit, the Bandwidth will be

A. 50 kHz B. 20 kHz C. 100 kHz D. infinite

42. In the circuit of figure, v1 = v2 = 10 V. Then

A. I1 = I2 B. I1 > I2 C. I2 > I1 D. I1 = 0

43. In a CE amplifier the ac cut off voltage is 9 V and slope of ac load line is - 0.5 mA/V. The ac saturation current is

A. 9 mA B. 4.5 mA C. 3 mA D. 18 mA

44. In a self bias circuit for CE amplifier, the emitter resistance is made three times the original value. The collector current will

A. remain the same B. become three times C. decrease D. become one-third

37

45. The main application of enhancement mode MOSFET is in

A. amplifier circuits B. oscillator circuits C. switching circuits D. all of the above

46. A potential of 7 V is applied to a silicon diode. A resistance of 1 kω is also connected in series. If the diode is forward biased, the current in the circuit is

A. 7 mA B. 6.3 mA C. 0.7 mA D. 0

47. In a voltage regulated power supply the zener operates in the breakdown region when (Vin is input voltage and Vz is zener breakdown voltage)

A. Vin < Vz B. Vin > Vz C. Vin = Vz D. both (a) or (b)

48. The disadvantage of direct coupled amplifiers is

A. drift B. large size of transistor C. low voltage gain D. both (b) and (c)

49. A differential amplifier consists of two CB amplifiers.

A. True B. False

50. The voltage gain of an amplifier without and with feedback are 100 and 20. The negative feedback is

A. 4% B. 5% C. 20% D. 80%

Answer of Analog digital : BJT amplifier, Zener

1‐>2 , 2‐>2 , 3‐>3 , 4‐>2 , 5‐>1 , 6‐>3 , 7‐>2 , 8‐>3 , 9‐>2 , 10‐>4 , 11‐>2 , 12‐>2 , 13‐>2 ,

14‐>4 , 15‐>4 , 16‐>1 , 17‐>1 , 18‐>3 , 19‐>2 , 20‐>4 , 21‐>3 , 22‐>3 , 23‐>4 , 24‐>1 , 25‐>1

, 26‐>1 , 27‐>1 , 28‐>1 , 29‐>1 , 30‐>1 , 31‐>2 , 32‐>3 , 33‐>2 , 34‐>4 , 35‐>3 , 36‐>1 , 37‐

>4 , 38‐>2 , 39‐>1 , 40‐>2 , 41‐>3 , 42‐>3 , 43‐>2 , 44‐>4 , 45‐>3 , 46‐>2 , 47‐>2 , 48‐>1 ,

49‐>2 , 50‐>1

38

Analog Electronics

Section4:Frequency,Diode

1. The output voltage waveform of a CE amplifier is fed to a dc coupled CRO. The trace on the screen will be

A. dc output voltage B. ac output voltage C. sum of dc and ac output voltage D. either (a) or (b)

2. In figure, VCC = + 30 V, R1 = 200 kω and R2 = 100 kω. If VBE = 0.7 V, the voltage a cross RE =

A. +20 V B. +19.3 V C. +10 V D. +9.3 V

3. Values of VT at 20°C for an ideal P-N diode

A. 25.27 mV B. 30.3 mV C. 23 mV D. 50 mV

4. The circuit in the given figure is

A. low pass filter B. high pass filter C. band Pass filter D. band reject filter

39

5. In figure if the transistor is cut off, the collector voltage is equal to

A. VCC B. 0.5 VCC

C.

D. Zero

6. A CE amplifier has re = 6 ω, β = 100 and a = 0.98. The input impedance is

A. 6 ω B. 100 ω C. 600 ω D. 98 ω

7. A 120 V, 30 Hz source feeds a half wave rectifier circuit through a 4 : 1 step down transformer, the average output voltage is

A. 30 V B. 13.5 V C. 10 V D. 7.07 V

8. A buffer amplifier should have

A. high output impedance and high input impedance B. high output impedance and low input impedance C. low output impedance an low input impedance D. low output impedance and high input impedance

9. In a BJT amplifier the power gain from base to collector is 4000. The power gain in dB is

A. 3.6 B. 36 C. 7.2 D. 72

40

10. In figure base current is 10 μA and βdc = 100. Then VE =

A. 5 V B. 10 V C. 15 V D. 20 V

11. As the ratio Rf/RL increases the efficiency of a rectifier increases.

A. True B. False

12. Assertion (A): An op-amp has high voltage gain, high input impedance and low output impedance

Reason (R): Negative feedback increases output impedance


13. For transistor 2 N 338 the manufacturer specifies Pmax = 100 mW at 250°C free air temperature and maximum junction temperature of 125°C. Its thermal resistance is

A. 10° C/W B. 100° C/W C. 1000° C/W D. 5000° C/W

14. An op-amp integrating circuit uses

A. an inductor B. a capacitor C. both inductor and capacitor D. none of the above

15. A transistor has a maximum power dissipation of 350 mW at an ambient temperature of 25°C. If derating factor is 2 mW/°C, the maximum power dissipation for 40°C ambient temperature is

A. 300 mW B. 330 mW C. 350 mW D. 380 mW

41

16. In figure which diode will conduct and what will be the value of V0?

A. D3, 1 V B. D1, 2 V C. D2, 5 V D. D1, 5 V

17. The Vo of the op-amp circuit shown in the given is

A. 11 Vi B. 10 Vi C. Vi D. zero

18. A Hartley oscillator is used for

A. very low frequencies B. radio frequencies C. micro wave frequencies D. audio frequency

42

19. In the figure, assume the op-amp is to be ideal. The output Vo if the circuit is

A. 10 cos (100t)

B.

C.

D.

20. A negative feedback can be of

A. 2 types B. 3 types C. 4 types D. only 1 type

21. Regulation of the DC power supply of 12 V, 100 mA is the effective resistance of power supply is 20 ω

A. 22% B. 131% C. 30% D. 20%

22. Assertion (A): In an op-amp the voltage gain and band width can be adjusted as per requirement

Reason (R): Large value capacitor can also be fabricated on a chip


23. In an RC phase shift oscillator, the total phase shift of the three RC lead networks is

A. 360° B. 180° C. 90° D. 0°

43

24. A full wave diode rectifier using centre tapped transformer has diodes with forward resistance of 50 ohms each. The load resistance of 50 ohms each. The load resistance is also 50 ohms. The voltage regulation is

A. 20% B. 50% C. 100% D. 200%

25. funity of an op-amp is about 1 kHz.

A. True B. False

26. If input frequency is 50 Hz, the frequency of output wave in a full wave diode rectifier circuit is

A. 25 Hz B. 50 Hz C. 100 Hz D. 200 Hz

27. In a class C power amplifier the input frequency of ac signal is 1 MHz. If tank circuit has C = 1000 pF, the value of L =

A. 25 μH B. 50 μH C. 100 μH D. 200 μH

28. The turn ratio of a transformer is 20:1, if a load of 10ω is connected across the secondary, what will be the effective resistance seen looking into the Primary?

A. 2 kω B. 4 kω C. 8 kω D. 32 kω

29. A half wave diode rectifier uses a diode having forward resistance of 50 ohms. The load resistance is also 50 ohms. Then the voltage regulation is

A. 20% B. 50% C. 100% D. 200%

30. A class A transformer coupled power amplifier is to deliver 10 W output. The power rating of transistor should not be less than

A. 5 W B. 10 W C. 20 W D. 40 W

31. An op-amp has

A. low input and output impedance B. low input impedance and high output impedance C. low output impedance and high input impedance D. high output impedance and high input impedance

44

32. Leakage current approximately doubles for every 10°C increase in the temperature of a transistor has ICBO = 400 nA at 25°C, then its leakage current at 80°C

A. 10 μA B. 18 μA C. 20 μA D. 15 μA

33. A CB amplifier has a = 0.98 and RL = 600 ω. If IE = 3.5 mA, the current gain is

A. 1 B. 0.98 C. 0.98 x 3.5

34. In the circuit of figure β = 100 and quiescent value of base current is 20 μA. The quiescent value of collector

current is

A. 0.2 μA B. 2 μA C. 2 mA D. 20 mA

35. An npn transistor has a Beta cutoff frequency fβ of 1 MHz, and a common emitter short circuit low frequency current gain β0 of 200. It unity gain frequency fT and the alpha cut off frequency fa2 respectively are

A. 200 MHz, 201 MHz B. 200 MHz, 199 MHz C. 199 MHz, 200 MHz D. 201 MHz, 200 MHz

45

36. A CB amplifier has IE = 3.5 mA, a= 0.98 and RL = 600 ω. The input impedance

A. 0.98 ω B. 0.025 ω

C.

D. 600 ω 37. In the circuit of figure v1 = 8 V and v2 = 0. Which diode will conduct (Assume ideal diodes)?


38. In Class C operation the collector current looks like

A. full sine wave B. half sine wave C. narrow pulses D. nearly half sine wave

39. For the amplifier circuit of figure, the h parameters of transistor are hib = 25 ω, hfb = 0.999, hob = 10-6 ω. The voltage gain is

A. 0.999 B. 1.98 C. 20 D. 400

46

40. In a CE amplifier circuit the dc voltage between emitter and ground

A. is always zero B. cannot be zero C. may or may not be zero D. is negative

41. It has been found that in a rectifier circuit with RC filter one RC section reduces ripple by 15%. Two RC sections are used in cascade the reduction in ripple would be

A. 15% B. 30% C. 150% D. 225%

42. A bridge diode circuit using ideal diodes has in input voltage of 20 sin ωt volts. The average and rms values of output voltage are

A.

B.

C.

D.

43. Assuming VCE sat = 0.2 V and β = 50, the minimum base current (IB) required to drive the transistor in the given figure to saturation is

A. 56 μA B. 140 μA C. 60 μA D. 3 μA

44. The slew rate of an ideal op-amp is

A. very slow B. slow C. fast D. infinitely fast

47

45. In a CE amplifier circuit the ac voltage between emitter and ground

A. is very high B. may be high or low C. is zero D. depends on circuit configuration

46. In figure, secondary winding has 40 turns. For maximum power transformer to 2 ohm resistance the number of turns in primary is

A. 20 B. 40 C. 80 D. 160

47. In calculating output impedance of an amplifier the source is replaced by an open circuit.

A. True B. False

48. An amplifier has open loop gain of 100, input impedance 1 kω and output impedance 100 ω. If negative feedback with β = 0.99 is used, the new input and output impedances are

A. 10 ω and 1 ω B. 10 ω and 10 kω C. 100 kω and 1 ω D. 100 kω and 10 ω

49. If the differential voltage gain and the common mode voltage gain of a differential amplifier are 48 dB and 2 dB respectively, then its common mode rejection ratio is

A. 23 dB B. 25 dB C. 46 dB D. 50 dB

48

50. In the op-amp circuit given in the figure, the load current iL is

A.

B.

C.

D.

Answer of Analog digital : Frequency, Diode

1‐>3 , 2‐>4 , 3‐>1 , 4‐>1 , 5‐>1 , 6‐>3 , 7‐>2 , 8‐>4 , 9‐>2 , 10‐>3 , 11‐>2 , 12‐>3 , 13‐>3 ,

14‐>2 , 15‐>3 , 16‐>3 , 17‐>4 , 18‐>2 , 19‐>1 , 20‐>3 , 21‐>4 , 22‐>3 , 23‐>2 , 24‐>3 , 25‐>2

, 26‐>3 , 27‐>1 , 28‐>2 , 29‐>3 , 30‐>3 , 31‐>3 , 32‐>2 , 33‐>2 , 34‐>3 , 35‐>1 , 36‐>3 , 37‐

>1 , 38‐>3 , 39‐>4 , 40‐>2 , 41‐>4 , 42‐>1 , 43‐>1 , 44‐>4 , 45‐>3 , 46‐>3 , 47‐>2 , 48‐>3 ,

49‐>3 , 50‐>1

49

Analog Electronics

Section5:Impedance,Amplifier

1. If a = 0.995, IE = 10 mA, ICO = 0.5 mA, then ICEO will be

A. 100 μA B. 25 μA C. 10.1 μA D. 10.5 μA

2. A voltage multiplier circuit, using diodes and capacitors is suitable for

A. high voltage high current device B. high voltage low current device C. low voltage low current device D. low voltage high current device

3. Heat sink results in

A. slower dissipation of heat to atmosphere B. faster dissipation of heat to atmosphere C. lower ambient temperature D. lower transistor power

4. The feedback technique employed in the following circuit is

A. voltage series feedback B. current series feedback C. voltage shunt feedback D. current shunt feedback

5. A diode can have a very high forward resistance.

A. True B. False

6. A voltage tripler circuit and voltage quadrupler circuit use identical components. Then

A. voltage regulation in both circuits will be same B. voltage regulation in both may or may not be same C. voltage regulation in quadrupler circuit will be better than in tripler circuit D. voltage regulation in quadrupler circuit will be poorer than in tripler circuit

50

7. Two CE stages are coupled through a capacitor. To calculate the quiescent base current of the two transistors, the capacitor is treated as

A. open circuit B. short circuit C. neither (a) nor (b) D. either (a) or (b)

8. As compared to a full wave diode rectifier circuit using centre tapped transformer, the bridge diode rectifier circuit has the main advantage of

A. higher current carrying capacity B. higher efficiency C. lower ripple factor D. lower PIV

9. The current through R1 is(If β = 99, VBE = 0.74 V)

A. 0.1 mA B. 0.35 mA C. 0.2 mA D. none

51

10. In figure, D1 turns on when

A. vi is more than V1 B. vi is less than V1 C. vi is between V1 and V2 D. none of the above

11. A dc power supply has no load voltage of 30 V and full load voltage of 25 V at full load current of 1 A. The output resistance and voltage regulation respectively are

A. 5 ω and 25% B. 25 ω and 20% C. 5 ω and 16.7% D. 25 ω and 16.7%

12. An increase in ambient temperature means that maximum power rating of transistor

A. will increase B. will decrease C. may increase or decrease D. may increase or remain the same

13. The output impedance of an ideal op-amp is

A. zero B. low C. high D. infinite

14. A transistor with a = 0.9 and ICBO = 10 μA is biased so that IBQ = 90 μA. Then ICQ will be

A. 910 mA B. 5 mA C. 5.25 mA D. 4.95 mA

15. The input to an op-amp integrating amplifier is a constant voltage. The output will be

A. a constant voltage B. a sawtooth wave C. a ramp D. ac voltage

52

16. Output of a phase splitter is

A. a pair of sine waves of unequal amplitude B. a pair of sine waves of equal amplitudes C. a pair of sine waves of equal amplitudes and opposite phase D. a pair of sine waves of unequal amplitudes and opposite phase

17. In a CE amplifier the dc load line is the same as ac load line when

A. ac collector resistance and dc collector resistance are equal B. ac collector resistance and dc emitter resistance are equal C. ac collector resistance is very high D. ac collector resistance is one half of dc collector resistance

18. In figure the cut in voltage of diode is 0.7 V and its bulk resistance is 20 ω. The peak value of circuit current of during positive and negative half cycles are

A. 10 mA and zero B. 9.12 mA and zero C. 9.3 mA and zero D. zero and 9.12 mA

19. A class C amplifier has input frequency of 200 kHz. If width of collector pulses is 0.1 μs, duty cycle is

A. 1% B. 2% C. 10% D. 20%

20. A BJT is said to be operating in saturation region if

A. both junctions are reverse biased B. both junctions are forward biased C. base emitter junction is forward biased and base collector junction is reverse biased D. base collector junction is forward biased and base emitter junction is reverse biased

21. If an amplifier with gain of - 100 and feedback of β = - 0.1 has a gain change of 20% due to temperature the change in gain of the feedback amplifier will be

A. 0.02% B. 2% C. 0.1% D. 0.01%

22. FET amplifier is more difficult to analyse than BJT amplifier.

A. True B. False

53

23. In figure the voltage drop across diode is 0.7 V. Then the voltage across diode during negative half cycle is

A. 10 V B. 9.3 V C. zero D. 10.7 V

24. A virtual ground is a ground for

A. voltage B. current C. both voltage and current D. voltage but not for current

25. In the circuit of the given figure, assume that the diodes are ideal and the meter is an average indicating ammeter, the ammeter will read

A. 0.4√2 A B. 0.4 A

C.

D. 0.4/p mA

54

26. Which one of the following is connect expression of id for figure?

A.

B. C. 0 D. id1 - id2

27. In a CE amplifier the ac emitter resistance

A. is zero B. is high C. is very high D. may have any value

28. Which of the following can be used as a buffer amplifier?

A. CE B. CC C. CB D. Both (a) and (c)

29. A buffer amplifier should have

A. high input impedance and low output impedance B. high input impedance and high output impedance C. low input impedance and high output impedance D. low input impedance and low output impedance

30. In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half of the secondary winding is 30 V. Then PIV is

A. 30 V B. 60 V C. 15 V D. 10 V

55

31. To bypass a 100 ohm emitter resistor at

A. 10 μF B. 100 μF C. 1000 μF D. 1 μF

32. In figure the approximate voltages of

A. base and emitter are - 8 V and - 7.3 V B. base and collector are - 8 V and - 5 V C. collector and emitter are - 5 V and - 7.3 V D. base, emitter and collector are - 8, - 7.3 and - 5 V

33. In the circuit of figure both diodes are ideal. If v1 = 10 V and v2 = 10 V which diode will conduct?


56

34. In figure, VG =

A. 2.22 V B. 22.2 V C. 0.22 V D. 0.022 V

35. In the following figure C = 0.02 μF, and Vth is known to be of frequency ω = 107 rad/sec and rd = 2.5 ω and ZTh = RTh = 10 ω Then phase angle between id and Vd

A. 26.5° B. 25° C. 30° D. 0°

36. If it is desired to have low output impedance in an amplifier circuit then we should use

A. common collector circuit B. common base circuit C. common emitter circuit D. either (b) or (c)

37. A Ge diode operated at a junction temperature of 27°C. For a forward current of 10 mA, VD is found to be 0.3 V. If VD = 0.4 V then forward current will be

A. 400 mA B. 475 mA C. 477 mA D. 480 mA

57

38. A second order active bandpass filter can be obtained by cascading LP second order filter having higher cut off frequency fOH with a second order HP filter having lower cut off frequency fOL provided

A. fOL < fOH B. fOL > fOH C. fOH = fOL D. fOH < 0.5 fOL

39. If the output current wave shape of class C circuit has a period of 1 μs and a pulse width of 0.006 μs, the duty cycle is

A. 6% B. 0.6% C. 0.006% D. 0.06%

40. The main advantage of CC amplifier is

A. High input impedance and low output impedance B. Low input impedance and high output impedance C. High voltage gain D. High current gain

41. Which configuration is suitable for impedance matching?

A. CB B. CE C. CC D. CB and CE

42. In a transistor the minimum and maximum values of βdc are 100 and 121. The proper value of βdc to be used to locate Q point is

A. 100 B. 121 C. 110.5 D. 110

43. In figure vi = 10 mV dc maximum. The maximum possible dc output offset voltage is

A. 60 mV dc B. 110 mV dc C. 130 mV dc D. 150 mV dc

58

44. The open loop gain of an amplifier is 50 but likely to decrease by 20% due to various factors. If negative feedback with β = 0.1 is used, the change in gain will be about

A. 20% B. 2% C. 0.5% D. 0.05%

45. Generally the gain of a transistor amplifier falls at high frequencies due to the

A. internal capacitance of device B. coupling capacitor at the I/P C. skin effect D. coupling capacitor at the O/P

46. A voltage gain of a CE amplifier connected in collector to base configuration is 50. Collector to base resistor RF = 1 kω, RC = 4ω, the O/P resistance R0 =?

A. 800 ω B. 813 ω C. 817 ω D. 819 ω

47. In a CE amplifier, the output voltage is equal to product of

A. ac collector current and ac collector resistance B. ac base current and ac collector resistance C. ac emitter current and ac emitter resistance D. ac collector current and source resistance

48. Assertion (A): In an RC coupled amplifier the junction capacitances can be neglected at low frequencies but not at high frequencies

Reason (R): Capacitive reactance is inversely proportional to frequency.


49. Assertion (A): In class C amplifier the efficiency is more than that for other classes of amplifiers

Reason (R): In class C amplifier we can get high efficiency over a wideband


59

50. For the circuit of figure the critical frequency is

A.

B.

C.

D.

Answer of Analog digital : Impedance, Amplifier

1‐>1 , 2‐>2 , 3‐>2 , 4‐>3 , 5‐>2 , 6‐>4 , 7‐>1 , 8‐>4 , 9‐>1 , 10‐>1 , 11‐>2 , 12‐>2 , 13‐>1 ,

14‐>1 , 15‐>4 , 16‐>3 , 17‐>3 , 18‐>2 , 19‐>2 , 20‐>2 , 21‐>2 , 22‐>2 , 23‐>1 , 24‐>4 , 25‐>4

, 26‐>1 , 27‐>1 , 28‐>2 , 29‐>1 , 30‐>2 , 31‐>3 , 32‐>1 , 33‐>3 , 34‐>1 , 35‐>1 , 36‐>1 , 37‐

>3 , 38‐>1 , 39‐>2 , 40‐>1 , 41‐>3 , 42‐>4 , 43‐>2 , 44‐>3 , 45‐>1 , 46‐>2 , 47‐>1 , 48‐>1 ,

49‐>3 , 50‐>2

60

Analog Electronics

Section6:Capacitor,Rectifier1. In the op-amp circuit of figure, V0 =

A. 10 V B. -10 V C. 5 V D. -5 V

2. An ideal op-amp requires

A. zero input offset voltage B. low input offset voltage C. high input offset voltage D. infinite input offset voltage

3. In figure, ID = 4 mA. Then VDS =

A. 20 V B. 16 V C. 4 V D. 0.4 V

61

4. In figure the zener has a resistance of 5 ohms. As the load resistance is varied, the output voltage

A. will remain constant at 12 V B. will vary between 12.05 and 12.65 V C. will vary from 10 to 20 V D. will remain constant at 12.05 V

5. The most widely used diode rectifier circuit is

A. half wave B. full wave with centre tapped transformer C. bridge D. either (a) or (b)

6. It is desired to reduce distortion in a CE amplifier circuit. We should

A. reduce emitter current B. reduce collector current C. reduce ac base voltage D. reduce base emitter voltage

7. In the circuit of figure β = 50 and VBE = 0.5 V. The quiescent value of base current IB is

A. about 28 μA B. about 28 mA C. about 0.28 μA D. about 2.8 A

8. In an amplifier the stray capacitances assume impedance at low frequencies

A. True B. False

62

9. In the diode circuit shown in figure the diodes are ideal. The impedance seen by source is

A. 1 k ohm B. 2 k ohm C. 0.5 k ohm D. infinite

10. In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half the secondary winding is 40 V. If diodes are ideal, the average output voltage is

A. 40 V B. 25.5 V C. 20 V D. 2.55 V

11. The main advantage of a crystal oscillator

A. can oscillate any frequency B. gives a high output voltage C. frequency of oscillation is almost constant D. can operates at a low dc voltage

12. An amplifier has input impedance of 4 kω and output impedance of 80 kω. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are

A. 40 kω and 8 kω respectively B. 4 kω and 80 kω respectively C. 0.4 kω and 800 kω respectively D. 8 kω and 160 kω respectively

13. In the circuit of figure diode will conduct

A. from 90 to 180° in the positive half cycle B. from 30° to 180° in the positive half cycle C. from 50° to 160° in the positive half cycle D. from 30° to 150° in the positive half cycle

14. The input to integrating op-amp is a rectangular wave. The output will be

A. a sine wave B. a rectangular wave C. a triangular wave D. none of the above

63

15. The purpose of connecting a coupling capacitor in the output circuit of an amplifier is

A. to increase voltage gain B. to increase collector current C. to block dc collector voltage D. all of the above

16. Which component is allowed to pass through it by a choke filter?

A. Dc B. Ac C. Both dc and ac D. Only high frequency ac

17. In CE amplifier the base current is very high.

A. True B. False

18. A 741 type op-amp has a gain bandwidth product of 1 MHz. A non-inverting amplifier using this op-amp and having a voltage gain of 20 dB will exhibit a -3dB bandwidth of

A. 50 kHz B. 100 kHz

C.

D.

19. In the CE circuit shown in figure the slope of ac load line will be

A.

B.

C.

D.

64

20. In a self bias circuit for CE amplifier, an increase in emitter resistance RE results in

A. increase in emitter voltage B. decrease in emitter voltage C. increase in emitter current D. decrease in emitter current

21. The JFET in the circuit shown in figure has an IDSS = 10 mA and Vp = -5V. The value of the resistance Rs for a drain current IDS = 6.4 mA is

A. 156 ω B. 470 ω C. 560 ω D. 1 kω

22. In the circuit of figure, PIV can be up to

A. Em B. 2 Em C. 0.5 Em D. 2√Em

65

23. The dc output voltage of the circuit is

A. 4.3 V B. 1.369 V C. 3.87 V D. 1.94 V

24. For a BJT if β = 50, ICEO = 3 μA and IC = 1.2 mA then IE

A. 1 mA B. 1.2 mA C. 1.3 mA D. 1.4 mA

25. It is desired to reduce distortion in an amplifier from 8% to 2% by using 5% negative feedback. The open and closed loop gains respectively are

A. 60 and 15 B. 15 and 60 C. 6 and 1.5 D. 1.5 and 6

26. The zener diode in the rectangular circuit shown in the figure has a zener voltage of 5.8 volts and a zener knee current of 0.5 mA. The maximum load current drawn from this circuit ensuring proper functioning over the input voltage range between 20 and 30 volts, is

A. 23.7 mA B. 14.2 mA C. 13.7 mA D. 24.2 mA

66

27. The circuit shown is

A. voltage series feedback amplifier B. transconductance amplifier C. transresistance amplifier with open circuit mutual resistance RF D. transresistance amplifier with short circuit mutual resistance RF

28. In a power amplifier the collector current flows for 270° of the input cycle. The operations is

A. class A B. class B C. class AB D. class C

29. In the graphical analysis of an amplifier circuit, the slope of dc load line depends on

A. load resistance only B. collector supply voltage only C. both load resistance and collector supply voltage D. none of the above

30. Consider 49 cascaded amplifiers having individual rise time as 2 n sec. 3 n sec. ... 50 n sec. The input waveform rise time is 1 n sec. Then the output signal rise time is given time by (Assume output signal rise time is measured within 10 percent range of the final output signal.)

A. 39 - 28 μsec B. 2.28 μsec C. 0.228 μsec D. 39.28 μsec

67

31. In figure, V0 =

A. -1 V B. 2 V C. +1 V D. +15 V

32. Percentage increase in the reverse saturation current of a diode if the temperature is increased from 25°C to 50°C

A. 50% B. 500% C. 565.7% D. 575.6%

33. The transistor of following figure in Si diode with a base current of 40 μA and ICBO = 0, if VBB = 6V, RE = 2 kω and β = 90, IBQ = 20 μA then IEQ =

A. 1800 μA B. 180 μA C. 2000 μA D. 3000 μA

34. A voltage doubler circuit is fed by a voltage Vm sin ωt. The output voltage will be nearly 2 Vm only if

A. load resistance is small B. load resistance is large C. load resistance is neither small nor large D. either (a) or (c)

68

35. The op-amp circuit shown in the figure is a filter. The type of filter and its cut off type of filter and its cut off frequency are respectively.

A. high Pass, 1000 rad/sec B. low Pass, 100 rad/sec C. high Pass, 10000 rad/sec D. low pass, 10000 rad/sec

36. A full wave rectifier supplies a load of 1 kω. The a.c. Voltage applied to the diodes is 220 - 0 - 220 Volts rms. If diode resistance is neglected, then Average d.c. Voltage

A. 220 V B. 200 V C. 198 V D. 0 volts

37. In figure we need an ac ground. The proper value of C is

A. 1000 μF B. 100 μF C. 10 μF D. 1 μF

38. In a capacitor filter, the time constant RLC should be small.

A. True B. False

69

39. A full wave rectifier circuit using centre tapped transformer, the input frequency 50 Hz. The frequency of output is

A. 100 Hz B. 50 Hz C. 25 Hz D. none of the above

40. When the circuit is switched on, the loop gain of a Wien bridge oscillator is

A. 1 B. more than 1 C. less than 1 D. about 0.5

41. For an npn transistor connected as shown in the figure VBE = 0.7 volts. Given that reverse saturation current of the junction at room temperature 300K is 10-13A, the emitter current.

A. 30 mA B. 39 mA C. 49 mA D. 20 mA

42. In a negative feedback amplifier A = 100, β = 0.04 and Vs = 50 mV, then feedback will be

A. 4 B. 8 C. 10 D. 2

43. In figure V0 =

A. 11 Vi B. 10 Vi C. Vi D. 0

70

44. In figure, V0 =

A. zero B. 5.7 V C. 6.9 V D. 12.6 V

45. For the circuit in figure the output wave shape is

A.

B.

C.

D.

71

46. In figure the current through resistor R

A. is always equal to 130 mA B. may vary between 130 mA and 10 mA C. may vary between 65 mA and 10 mA D. is always equal to 65 mA

47. In figure, ID = 4 mA. Then VS =

A. 20 V B. 16 V C. 6 V D. 0.6 V

48. In the graphical analysis of CE amplifier circuit, the upper end of load line is called

A. saturation point B. cut off point C. Q point D. none of the above

72

49. In figure, V0 =

A. 20 V B. 10 V C. 5 V D. 0

50. If the midband gain of an amplifier is 40 dB, the gain at half power frequency is

A. 37 dB B. 30 dB C. 20 dB D. 13 dB

Answer of Analog digital : Capacitor, Rectifier

1‐>2 , 2‐>1 , 3‐>3 , 4‐>2 , 5‐>3 , 6‐>4 , 7‐>1 , 8‐>2 , 9‐>1 , 10‐>2 , 11‐>3 , 12‐>1 , 13‐>4 ,

14‐>3 , 15‐>3 , 16‐>1 , 17‐>2 , 18‐>2 , 19‐>2 , 20‐>4 , 21‐>1 , 22‐>2 , 23‐>2 , 24‐>2 , 25‐>1

, 26‐>4 , 27‐>3 , 28‐>3 , 29‐>1 , 30‐>3 , 31‐>2 , 32‐>3 , 33‐>1 , 34‐>2 , 35‐>1 , 36‐>3 , 37‐

>1 , 38‐>2 , 39‐>1 , 40‐>2 , 41‐>3 , 42‐>1 , 43‐>3 , 44‐>3 , 45‐>4 , 46‐>1 , 47‐>3 , 48‐>1 ,

49‐>4 , 50‐>1

73

Analog Electronics

Section7:FET,Wienbridge

1. A bridge rectifier circuit has a dc load current of 10 mA and a filter capacitance of 1000 μF. The peak to peak ripple voltage is

A. 0.01 V B. 0.05 V C. 0.1 V D. 0.5 V

2. Which of the following best represents the bandwidth of an actual op-amp?

A. 100 Hz to 1 MHz B. 0 Hz to 100 kHz C. 0 Hz to 10 MHz D. 0 Hz to infinity

3. In a N-P-N transistor, when emitter junction is forward biased and collector junction is reverse biased, the transistor will operate in

A. active region B. saturation region C. cut of region D. inverted region

4. An engineer designs an amplifier to have a voltage gain of 60, but when constructed it only had a gain of 50. What percentage of feedback will cause oscillations?

A. 0.1% B. 0.5% C. 1% D. 2%

5. In figure the input and output Miller capacitances are

A. 0.25 μF each B. 500 pF each C. 0.25 μF and 500 pF respectively D. 500 pF and 0.25 μF respectively

6. IF VCC = 15 V, VCEQ = 5 V and ICQ = 50 mA, the efficiency in class A operation is

A. 100% B. 50% C. 25% D. 16.7%

74

7. In a FET, gm varies as

A. IDS B. IDS2 C. 1/IDS D.√IDS

8. he most common method for biasing a JFET is

A. reverse bias B. self bias C. voltage divider bias D. none of the above

9. Ultra high frequency oscillators work in the range

A. 20 Hz to 20 kHz B. 1 kHz to 30 kHz C. 30 kHz to 30 MHz D. above 30 MHz

10. The voltage eo indicated in the figure has been measured by an ideal voltmeter. Which of the following can be calculated?

A. Bias current of inverting input only B. Bias current of inverting and non-inverting inputs only C. Input offset current only D. Both the bias currents and the I/P offset current

11. The element in the feedback circuit of a logarithmic amplifier using op-amp is

A. a resistor B. a capacitor C. an inductor D. a diode

75

12. In figure gain bandwidth product is

A. 200 Hz B. 200 MHz C. 200 kHz D. 2 MHz

13. An inverting amplifier has R1 = 10 kω, and Rf = 150 kω then the O/P voltage, if input voltage Vi = 1 volt.

A. -15 V B. -10 V C. 15 V D. -14 V

14. For an ideal noise free transistor amplifier the noise factor is

A. zero B. zero dB C. 1 dB D. depends on other factors

15. If a class C power amplifier has an input signal with frequency of 200 kHz and the width of collector current pulses of 0.1 ms, then the duty cycle of the amplifier will be

A. 1% B. 2% C. 10% D. 20%

16. At midband frequencies the coupling capacitor in RC coupled CE amplifier may be considered as

A. open circuit B. short circuit C. a reactance equal to load resistance D. none of the above

17. Typical values of current gains for CE, CB and CC amplifiers are

A. 120, 120 and 1 respectively B. 120, 1 and 120 respectively C. 1, 120 and 120 respectively D. 1, 1 and 120 respectively

76

18. Which op-amp circuit uses a capacitor in series with input and resistance in feedback path?

A. Differentiating amplifier B. Integrating amplifier C. Logarithmic amplifier D. None of the above

19. A Wien bridge is suitable for

A. audio frequencies only B. radio frequencies only C. both audio and radio frequencies D. very low frequencies only

20. Voltage VL in the circuit when Vs < 0 where D is an ideal diode. (Take R1 = Rs = RL = 1 ω)

A. 0 B. 1 C. 1.5 D. cannot find

21. Consider the following statements A totem pole configuration used in the output stage if an op-amp has the advantage of using

Only n-p-n BJTs Complementary symmetrical pair of transistors Only one transistor Which of these statements is/are correct?

A. 1 alone B. 2 alone C. 3 alone D. 1 and 3

77

22. When Z1 << Z, The circuit of figure works as

A. inverting amplifier B. Schmitt trigger C. non-inverting amplifier D. source follower

23. In a crystal

A. the frequencies of series and parallel resonance are equal B. the frequency of series resonance is more than frequency of parallel resonance C. the frequency of parallel resonance is more than frequency of series resonance D. None of the above

24. he signal input to a given amplifier is made up of 100 mω signal power and 1 mω noise power. The amplifier contributes an additional 100 mω of noise and has a power gain of 20 dB. The noise factor is

A. 1 B. 1.5 C. 2.0 D. 15

25. In feedback amplifier the closed loop gain is nearly independent of open loop gain and depends only on the feedback factor.

A. True B. False

26. Class C amplifier is suitable for

A. a narrow frequency band B. a wide frequency band C. audio frequencies D. either (b) or (c)

78

27. For the amplifier in figure, β = 800. The mid-band voltage gain V0/Vi is

A. 0 B. < 1 C. ≈ 1 D. 800

28. The minimum gate source voltage that creates the n-type inversion layer is called

A. cut off voltage B. on voltage C. threshold voltage D. zener voltage

29. The h parameter equivalent circuit of BJT has one voltage source and one current source.

A. True B. False

30. Which of the following figures is an ideal equivalent circuit of a n-p-n transistor?

A. figure A B. figure B C. figure C D. none

31. Assertion (A): An op-amp amplifier can amplify dc signal

Reason (R): An op-amp amplifier is a direct coupled amplifier


79

32. In the circuit of figure, the value of re is (neglecting vbe)

A. 100 ω B. 75 ω C. 50 ω D. 25 ω

33. A feedback network to be used with an amplifier to provide oscillation is tested and found to give an output of 0.124 V with a 0.5 V input. What percentage negative feedback should be introduced to the amplifier so that linear oscillations result?

A. 1.25% B. 2.50% C. -1.25% D. -2.5%

34. In a class C operation VCC = 40 V, RL = 50 ω. The maximum load power can be

A. 64 W B. 32 W C. 16 W D. 8 W

35. N-channel FETs are superior to p-channel FETs because

A. mobility of electrons is smaller than that of holes B. mobility of electrons is greater than that of holes C. they consume less power D. they have high switching time

36. For a push pull circuit the most favoured biasing method is

A. self bias B. emitter bias C. diode bias D. collector bias

37. When the emitter current of a transistor is changed by 1 mA, its collector current changes by 0.990 mA. The common-emitter short-circuit current gain is

A. 1 B. 199 C. 99 D. 9.9

80

38. In a transistor amplifier, the reverse saturation current ICO

A. Doubles for every 10°C rise in temperature B. Doubles for every 20°C rise in temperature C. Increase 100°C with temperature D. Doubles for every 5°C rise in temperature

39. To draw ac equivalent circuit for a CE amplifier we should

A. Reduce all dc sources to zero B. Short all capacitors C. Reduce all dc sources to zero and short all capacitors D. Reduce all dc sources to zero and open all capacitors

40. In an RC-coupled amplifier for improving the low frequency response

A. lower RL is provided B. more bias is used C. less gain is provided D. higher CC is used

41. The bandwidth of an amplifier is BW, of n-stage of such as amplifier are cascaded, the bandwidth will become

A. n BW

B.

C.

D.

42. The advantage of Weinbridge oscillator over the phase shift oscillator is that oscillator the frequency may be varied over a range of

A. 1 : 2 B. 1 : 3 C. 1 : 5 D. 1 : 10

43. Figure uses 10 V zener diode. The minimum and maximum current through series resistance are

A. 10 mA and 30 mA B. 20 mA and 40 mA C. 0 and 30 mA D. 0 and 40 mA

81

44. An ideal voltage amplifier should have

A. low input impedance and high output impedance B. high input impedance and low output impedance C. high input impedance and high output impedance D. low input impedance and low output impedance

45. Assertion (A): Class A and Class B amplifier predominate in audio applications.

Reason (R): Class C amplifier is used at radio frequencies.


46. Assertion (A): The gain of an FET amplifier can be changed by changing gm

Reason (R): Most receivers use automatic gain control to counteract changes in volume caused by fading


47. In a N-P-N transistor, when emitter junction is forward biased and collector junction is reverse biased the transistor will operate in

A. active region B. saturation region C. cut-off region D. inverted region

48. For class B operation the theoretical maximum efficiency is

A. 100% B. 78.5% C. 50% D. 27.5%

49. The circuit of figure is

A. Precision integrator B. Hartley oscillator C. Butterworth high pass filter D. Wien bridge oscillator

82

50. In the circuit of figure, v0 =

A. 3 v1 + 4 v2 B. -3 v1 - 4 v2 C. 4 v1 + 3 v2 D. -4 v1 - 3 v2

Answer of Analog digital : FET, Wien bridge

1‐>3 , 2‐>2 , 3‐>1 , 4‐>4 , 5‐>1 , 6‐>4 , 7‐>4 , 8‐>2 , 9‐>4 , 10‐>3 , 11‐>2 , 12‐>3 , 13‐>1 ,

14‐>2 , 15‐>4 , 16‐>2 , 17‐>2 , 18‐>1 , 19‐>1 , 20‐>1 , 21‐>1 , 22‐>4 , 23‐>3 , 24‐>3 , 25‐>1

, 26‐>1 , 27‐>3 , 28‐>3 , 29‐>1 , 30‐>2 , 31‐>1 , 32‐>4 , 33‐>3 , 34‐>3 , 35‐>2 , 36‐>3 , 37‐

>3 , 38‐>1 , 39‐>3 , 40‐>4 , 41‐>4 , 42‐>4 , 43‐>1 , 44‐>2 , 45‐>2 , 46‐>2 , 47‐>1 , 48‐>2 ,

49‐>4 , 50‐>2

83

Analog Electronics

Section8:CrystalOscillator,Resistance

1. The properties of FETs closely resemble those of a

A. thermionic valve B. P-N-P transistor C. N-P-N transistor D. UJT

2. Which of the following is not valid in case of FETs?

A. It has low voltage gain B. It has high input impedance C. It has fast switching time D. It is voltage controlled device

3. The purpose of providing groundings rings with MOSFET is to

A. avoid any stray voltage at the gate that may destroy SiO2 layer B. protect against any descaling C. ground all eddy currents D. protect against any physical injury

4. The RC network of wein bridge oscillator consists of resistors and capacitors of values R = 220 kω and C = 250 PF Determine the frequency of oscillation

A. 2.98 kHz B. 3 kHz C. 2 kHz D. 10 kHz

5. Which of the following device acts as an N-P-N and a P-N-P transistor connected base to base and emitter to controller?

A. UJT B. SCR C. Diac D. Triac

6. A FET is a better clapper than a BJT because it has

A. lower off-set voltage B. higher series ON resistance C. lower input current D. higher input impedance

7. An op-amp uses

A. RC coupling B. direct coupling C. transformer coupling D. either (b) or (c)

84

8. In a single stage differential amplifier, the output offset voltage is basically dependent on the mismatch of

A. VBE, IB and β B. VBE and IB C. IB and β D. VBE and β

9. A voltage tripler circuit uses

A. 2 diodes and 2 capacitors B. 3 diodes and 3 capacitors C. 2 diodes and 3 capacitors D. 3 diodes and 2 capacitors

10. In which configuration is ac collector voltage zero?

A. CE B. CB C. CC D. none of the above

11. Which of the following amplifier circuits has highest input impedance?

A. Circuit using BJT B. Circuit using JFET C. Circuit using MOSFET D. Either (a) or (b)

12. A second-order band-pass active filter can be obtained by cascading a low pass second order section having cut off frequency fOH with a high pass second order section having cut-off frequency fOL provided

A. fOH > fOL B. fOH < fOL C. fOH = fOL D. fOH ≤ 1/2fOL

13. The input gate current of FET is closer to

A. few amperes B. few milli amperes C. few microamperes D. negligibly smaller value

14. Which connection is rarely used?

A. CE B. CB C. CC D. Both (a) and (b)

85

15. Assertion (A): Transformer coupling has the disadvantage of the weight of transformer and Saturation of core

Reason (R): Transformer coupling is very suitable for impedance matching


16. The ripple factor of a power supply is

A.

B.

C.

D.

17. 3N 200 is a

A. semi-conductor diode B. P-N-P transistor C. dual gate MOSFET D. UJT

18. In a biased limiter the clipping level can be adjusted by adjusting the voltage of battery.

A. True B. False

19. In a CE amplifier, the collector resistance is 6 kω and load resistance is 3 kω. The ac load resistance is

A. 9 kω B. 6 kω C. 3 kω D. 2 kω

20. In a class C operation VCC = 30 V and VCE(sat) = 2 V. The efficiency is

A. 93.75% B. 88% C. 6.66% D. 3.33%

21. When a 1 V increase in gate voltage changes the drain current 10 mA in an FET, its gm equals

A. 10 μμ B. 100 μμ C. 1000 μμ D. 10000 μμ

86

22. When the emitter current of a transistor is changed by 1 mA, its collector current changes by 0.990 mA. The common base short circuit current gain a for the transistor is

A. 0.99 B. 1.01 C. 1.001 D. 0.990

23. Assertion (A): A common collector amplifier is used for matching a high impedance source to a low impedance load

Reason (R): A common collector amplifier has a near unity voltage gain


24. The current ICBO flows in

A. base and emitter leads B. base and collector leads C. collector and emitter leads D. collector, emitter and base leads

25. In a crystal oscillator of the Colpitt's oscillator type, the crystal is put is place of the

A. resistor R1 B. condenser C2 C. condenser C1 D. inductor L

26. Class A and Class B power amplifiers predominate at

A. audio frequencies B. radio frequencies C. all frequencies D. audio and radio frequency

27. Astable multivibrator has

A. one stable state B. two stable state C. two quasi-stable states D. one quasi stable state

28. Most small signal transistors are

A. N-P-N, silicon, in a plastic package B. P-N-P, silicon, in a plastic package C. N-P-N, germanium in a metallic case D. P-N-P, germanium in a metallic case

29. A Hartley oscillator is used for generation

A. very low frequency oscillation B. radio frequency oscillation C. microwave oscillation D. audio-frequency oscillation

87

30. In voltage amplifiers, the load resistance

A. should be a small as possible B. should be as large as possible C. must be equal to output impedance D. must be half of output impedance

31. Which of the following method cannot be used to increase the bandwidth for cascaded RF amplifier stages?

A. Wave traps in each stage B. Stagger tuning C. A shunt damping resistor across each tuned circuit D. Doubled tuned transformers with tighter coupling

32. For a transistor amplifier with self biasing network, the following components are used. R1 = 4 kω, R2 = 4 kω, RC = 1 kω. The approximate value of the stability factor 'S' will be

A. 4 B. 3 C. 2 D. 1.5

33. Which of the following statement is correct?

A. FET and junction transistor both are unipolar B. FET and junction transistor both are bipolar C. The FET is bipolar, while junction transistor are unipolar D. The FET is unipolar, while junction transistor are bipolar

34. Assertion (A): The main use of positive feedback is in oscillator circuits.

Reason (R): In an oscillator the loop gain Aβ is kept slightly more than unity


35. Self bias is an example of __________ feedback that tends to stabilize the drain current against changes in temperature and JFET replacement.

A. variable B. low C. negative D. positive

36. The minimum value of hfe of a transistor used in RC phase shift oscillator is

A. 54.4 B. 45.4 C. 44.5 D. 29

37. In a transistor which of the following region is very lightly doped and is very thin?

A. Emitter B. Base C. Collector D. None of the above

88

38. Transformer coupling is mostly used in

A. RF amplifier B. audio amplifier C. both audio and RF amplifier D. none of the above

39. In every practical oscillator the loop gain is slightly more than unit and amplitude of oscillations is limited by

A. magnitude of loop gain B. onset of non-linearity C. magnitude of gain D. β

40. In figure the dc load line will meet the y and x axis respectively at

A. 20 mA and 30 V B. 15 mA and 20 V C. 25 mA and 40 V D. 10 mA and 20 V

41. The h parameter h11 is the same in CE and CC circuit.

A. True B. False

42. The properties of JFET resemble those of

A. thermionic values B. N-P-N transistors C. P-N-P transistors D. unijunction transistor

43. A sine wave is passed through an amplifier which severely limits it symmetrically. If then passes to a second amplifier which is narrow band and tuned to the frequency of the original sine wave. What will be the output wave from this second amplifier?

A. A square wave of the same frequency as that of the original sine wave B. A square wave of double the frequency of that of original sine wave C. A sine wave of constant amplitude at the frequency of the original sine wave D. A sine wave of constant amplitude at double frequency of the original sine wave

89

44. In the circuit shown in the given figure, the current flowing through resistance of 100 ω would be

A. 8 mA B. 10 mA C. 20 mA D. 100 mA

45. The gate electrode in the FET corresponds to the

A. collector in a bipolar transistor B. base in a bipolar transistor C. emitter in a bipolar transistor D. none of the above

46. In a CE class A amplifier the quiescent current and voltage are ICQ and VCEQ. The maximum power output can be

A. (VCEQ)(ICQ)

B.

C.

D. 2 (VCEQ)(ICQ)

47. In a P-N-P junction transistor as compared to base region is more heavily doped so that

A. leakage current is minimized B. recombination will be increased in the base region C. the flow across the base regional is only because of electrons D. the flow across the base region is mainly because of holes

48. One input terminal of high gain comparator circuit is connected to ground and a sinusoidal voltage is applied to the other input. The output of comparator will be

A. sinusoidal B. full rectified sinusoidal C. half rectified sinusoidal D. square wave

90

49. In figure Vi may vary from 15 to 20 V and load current may vary from 20 mA to 100 mA. Suitable maximum value of R is

A. 20 ω B. 50 ω C. 100 ω D. 200 ω

50. The A.C. resistance of the emitter diode will be

A. 5.05 ω B. 50.5 ω C. 505 ω D. 5050 ω

Answer of Analog digital : Crystal Oscillator, Resistance

1‐>1 , 2‐>3 , 3‐>1 , 4‐>1 , 5‐>2 , 6‐>1 , 7‐>2 , 8‐>3 , 9‐>2 , 10‐>3 , 11‐>3 , 12‐>1 , 13‐>4 ,

14‐>2 , 15‐>2 , 16‐>2 , 17‐>3 , 18‐>1 , 19‐>4 , 20‐>1 , 21‐>4 , 22‐>1 , 23‐>2 , 24‐>2 , 25‐>4

, 26‐>1 , 27‐>3 , 28‐>1 , 29‐>4 , 30‐>2 , 31‐>1 , 32‐>2 , 33‐>4 , 34‐>2 , 35‐>3 , 36‐>3 , 37‐

>2 , 38‐>3 , 39‐>2 , 40‐>1 , 41‐>1 , 42‐>2 , 43‐>3 , 44‐>1 , 45‐>2 , 46‐>2 , 47‐>4 , 48‐>4 ,

49‐>2 , 50‐>2

91

Analog Electronics

Section9:Coupling

1. High cut off frequency can be expected in case of

A. common-base B. common-emitter C. common-collector D. all of the above

2. The MOSFET is almost ideal as a switching device because

A. it has linear characteristics B. it works progressively C. it consumes low power D. it has longer life

3. Assertion (A): A tuned amplifier uses a parallel tuned circuit

Reason (R): A tuned amplifier is used to amplify a narrowband frequencies


4. Assertion (A): If we overdrive an amplifier the output signal may get clipped

Reason (R): To dissipate heat to atmosphere a heat sink is sometimes attached to the case of transistor


5. Drain feedback bias is often used with

A. D MOSFETs B. E MOSFETs C. both D and E MOSFETs D. neither D nor E MOSFETs

6. For a transistor to have-a larger β it must have and a

A. close to zero B. close to 0.5 C. close to unity D. nearly infinite

92

7. In a self bias circuit for CE amplifier the collector supply voltage is made twice. The collector current will

A. decrease B. increase C. remain the same D. increase or decrease

8. In a CE amplifier circuit the emitter by pass capacitor is remove. The ac output voltage

A. increases B. remains the same C. increases or decreases D. decreases

9. JFET has __________ degree of isolation between input and output, and a __________ noise figure.

A. low, low B. high, high C. low, high D. high, low

10. JFET is also known as

A. linear device B. square law device C. inverse law device D. logarithmic law device

11. Pick the odd-one out

A. Hartley Oscillator B. Colpitt oscillator C. Clapp oscillator D. Weinbridge oscillator

12. Assertion (A): The duty cycle of a class C amplifier affects the power dissipation of transistor

Reason (R): At higher harmonics the efficiency of a class C amplifier becomes poor


13. The voltage gains of an amplifier without feedback and with negative feedback respectively are 100 and 20. The percentage of negative feedback (β) would be

A. 40% B. 5% C. 20% D. 80%

14. In a transistor βdc is likely to vary between 100 and 400. The proper value of βdc to be used to located Q point is

A. 100 B. 400 C. 250 D. 200

93

15. Which of the following noise becomes of great importance at high frequencies?

A. Shot noise B. Agitation noise C. Flicker noise D. Transit time noise

16. In a class C amplifier, full cycle conductor of the current is achieved by employing

A. tuned circuit B. transformers C. complementary pair D. Push pull configuration

17. In a differential amplifier, CMRR can be improved by using an increased

A. emitter resistance B. collector resistance C. power supply voltages D. source resistance

18. Figure shows a

A. JFET B. n-channel MOSFET C. p-channel MOSFET D. none of the above

19. Which of the following statement is false?

A. The gate of DMOSFET may be biased positively, zero or negatively B. N-channel enhancement-only MOSFET conducts only when its gate is highly positive C. JFET has lower input impedance than MOSFET D. The bipolar base is forward biased, JFET gate must also be forward biased

20. A generator with an internal resistance of 600 ω drives an amplifier whose input resistance is 400 ω. The generator's open circuit voltages is 1 mV; the amplifier develops 100mV across an 8kω load. The input voltage to the amplifier is

A. 0.1 m V B. 0.4 m V C. 1 m V D. 4 m V

21. Three cascaded stages have gains of 10, 20 and 25. The overall gain will be

A. 10 B. 55 C. 500 D. 5000

94

22. In an amplifier, if the output current flows for 120° of the input cycle, the class of amplifier will be

A. A B. B C. C D. AB

23. Assertion (A): The main use of Miller integrator is to generate ramp

Reason (R): An inverting amplifier can handle more than one input at the same time.


24. The knee voltages in silicon and germanium diodes respectively are

A. 0.3 V and 0.7 V B. 0.7 V and 0.3 V C. 0.7 V each D. 0.3 V each

25. In figure, IC ≈

A. I1 B. IB C. 0.5 I1 D. 0.5 IB

26. Turn off time of a transistor switch is equal to (where ts is storage time and tf is fall time.)

A. ts + tf B. ts - tf C. 2ts D. 2tf

27. The input and output signals for CE amplifier are always

A. equal B. in phase C. out of phase D. complementary to each other

95

28. Tuned amplifiers are used at radio frequencies.

A. True B. False

29. A differentiating amplifier has capacitor in the input path.

A. True B. False

30. From a measurement of the rise time of the output pulse of an amplifier whose input is a small amplitude square wave, one can estimate the following parameter of the amplifier

A. gain bandwidth product B. slew rate C. upper 3 dB frequency D. lower 3 dB frequency

31. If ac resistance of diode is re, then In CE, BJT amplifier the input impedance is

A. re B. β re C. (βre)

2

32. If the op-amp in figure has a unity gain frequency of 1 MHz, the cut off frequency is

A. 100 kHz B. 1 MHz C. 10 MHz D. 90 MHz

33. Which coupling produces the minimum interference with frequency response?

A. RC coupling B. Transformer coupling C. Direct coupling D. Impedance coupling

34. Find the odd one out

A. sweep voltage generator B. multivibrators C. sine wave oscillators D. blocking oscillators

96

35. CMRR of a difference amplifier is equal to

A. (Av')/(Acom) B. Av/Acom C. Acom/Av' D. (Av)/(Acom)2

36. In a P-N-P transistor, electrons flow

A. into the transistor at the collector only B. into the transistor at the base and the collector leads C. out of the transistor at base and collector leads D. out of the transistor at base, collector as well as emitter leads

37. Which of the following statement about TRIAC is incorrect?

A. It is not particularly suited to A.C. or mains power control B. Any one of its main terminals can be used either as cathode or as anode C. It can be triggered in response to both positive and negative gate terminals D. None of the above

38. In a CE amplifier the output coupling capacitor is short circuited. The dc collector voltage

A. will increase B. may increase or decrease C. will remain the same D. will decrease

39. In a one pole active low pass filter, the cut off frequency is fc. Then

A. gain decreases at the rate of 20 dB per decade increase in frequency above fc B. gain decreases at the rate of 20 dB per decade decrease in frequency below fc C. gain decreases at the rate of 40 dB per decade increase in frequency above fc D. gain decreases at the rate 40 dB per decade decrease in frequency below fc

40. In a full wave voltage doubler circuit, the input frequency is 560 Hz. The ripple frequency is

A. 25 Hz B. 50 Hz C. 100 Hz D. 200 Hz

41. Which op-amp circuit uses a diode as one of the circuit components?

A. Integrating amplifier B. Differentiating amplifier C. Logarithmic amplifier D. Summing amplifier

42. Overall efficiency of class B amplifier is

A. 72% B. 75% C. 78.5% D. 70%

97

43. Thermal run away of a transistor occurs when

A. heat dissipation from transistor is excessive B. transistor joints melt due to high temperature C. there is excessive leakage current due to temperature rise D. none of the above

44. The advantage of FET over BJT is

A. high input impedance B. lower noise C. no thermal runaway D. all of the above

45. Higher order active filters are used for variable

A. bandwidth B. gain in the pass band C. impedance D. roll off rate

46. The ac collector current is nearly equal to

A. ac base current B. ac signal current C. ac supply current D. ac emitter current

47. The equivalent circuit shown in figure is for

A. CE B. CB C. CC D. None of the above

48. In calculating input impedance, the load impedance is considered to be connected at the output.

A. True B. False

49. A half wave diode rectifier and full wave diode bridge rectifier both have an input frequency of 50 Hz. The frequencies of outputs respectively are

A. 100 Hz and 50 Hz B. 50 Hz and 100 Hz C. 100 Hz each D. 50 Hz each

98

50. Assertion (A): A sine wave with slew rate distortion looks rectangular

Reason (R): The maximum rate of output voltage change is called slew rate


Answer of Analog digital : Coupling

1‐>3 , 2‐>3 , 3‐>1 , 4‐>2 , 5‐>2 , 6‐>3 , 7‐>2 , 8‐>4 , 9‐>4 , 10‐>2 , 11‐>4 , 12‐>2 , 13‐>1 ,

14‐>4 , 15‐>4 , 16‐>1 , 17‐>1 , 18‐>2 , 19‐>4 , 20‐>2 , 21‐>4 , 22‐>3 , 23‐>2 , 24‐>2 , 25‐>1

, 26‐>1 , 27‐>3 , 28‐>1 , 29‐>1 , 30‐>3 , 31‐>2 , 32‐>1 , 33‐>3 , 34‐>3 , 35‐>1 , 36‐>2 , 37‐

>1 , 38‐>4 , 39‐>1 , 40‐>3 , 41‐>3 , 42‐>3 , 43‐>3 , 44‐>4 , 45‐>4 , 46‐>4 , 47‐>3 , 48‐>1 ,

49‐>2 , 50‐>4

99

Analog Electronics

Section10:CEamplifier,JEFT1. Symbol shown in figure represents a

A. P-channel enhancement MOSFET B. N-channel DEMOSFET C. UJT with P-type base D. UJT with N-type base

2. For holding the drain current constant in spite of large changes in JFET parameters

A. current source bias is used B. voltage divider bias is used C. reverse bias is used D. no bias is used

3. The feedback resistance rd in small signal model of MOSFET is of the order of

A. 1000 Mω B. 1 Mω C. 1 Kω D. 100 ω

4. An inverting voltage feedback is a

A. voltage amplifier B. current amplifier C. current to voltage converter D. voltage to current converter

5. A certain transistor has adc of 0.98 and a collectors leakage current of 5 μA. If IE = 1 mA, the collector current will be

A. 1.005 mA B. 0.985 mA C. 0.975 mA D. 0.955 mA

6. A Darlington circuit is obtained by connecting

A. two CB stages in cascade B. two CE stages in cascade C. a CE stages followed by CB stage D. two emitter follower in cascade

100

7. If the value of C2 and C3 are doubled, the oscillation frequency will be

A. quadrupled B. doubled C. unchanged D. halved

8. IN 3242 is a

A. P-N-P transistor B. N-P-N transistor C. UJT D. semi-conductor diode

9. Which of the following configuration has low thermal stability?

A. CB B. CC C. CE D. All have identical thermal stability

10. In an op-amp comparator, the positive or negative output is

A. saturated B. amplifier C. unsaturated D. any of the above

11. The input differential stage of op-amp. 741 is baised at about 10 μA current such a low current of the input stage gives

high CMRR high differential gain low differential high input impedance Which of these are correct?

A. 1 and 2 B. 1, 2 and 4 C. 3 and 4 D. 1, 2, 3 and 4

12. A clamper

A. adds a dc component to the input signal B. removes signal voltages above or below a specified value C. both (a) and (b) D. either (a) or (b)

13. Assertion (A): In Darlington pair, the overall β is product of individual βs

Reason (R): The voltage gain of a base driven amplifier is equal to ac collector voltage divided by ac base voltage


101

14. Efficiency of class A power amplifier is very poor.

A. True B. False

15. A CE amplifier has a high input signal. In the wave shape of emitter current

A. positive and negative half cycles will be symmetrical B. positive half cycle will be elongated and negative half cycle will be compressed C. positive half cycle will be compressed and negative half cycle will be elongated D. the half cycles may be either elongated or compressed

16. The use of a capacitor filter in a rectifier circuit gives satisfactory performance only when the load

A. current is high B. current is low C. voltage is high D. voltage is low

17. The heat sink disposes off heat mainly by

A. radiation B. natural convection C. forced convection D. conduction

18. In figure, current gain is

A. a B. re

C.

D.

19. In a series regulated power supply circuit the voltage gain of pass transistor satisfies the condition

A. Av → ∞ B. 1 << Av → ∞ C. Av ≈ 1 D. Av << 1

102

20. The ideal op-amp has the following characteristics

A. Ri = ∞, A = ∞, R0 = 0 B. Ri = 0, A = ∞, R0 = 0 C. Ri = ∞, A = 0, R0 = 0 D. Ri = 0, A = ∞, R0 = ∞

21. In oscillator circuits the energy feedback to its input terminal from output is

A. always in phase with the input signal B. 90° out of phase with the input signal C. 180° out of phase with the input signal D. 270° out of phase with the input signal

22. A cascade amplifier will have higher cut off frequency

A. equal to that of single stage amplifier B. less than that of single stage amplifier C. more than that of single stage amplifier D. none of these

23. A major advantage of TWT over a Klystron lies in its

A. higher bandwidth B. higher gain C. higher frequency D. higher output

24. In a CE amplifier the Q point is very close to cutoff point on the load line. This results in

A. saturation clipping B. cut off clipping C. both saturation and cut off clipping D. either saturation clipping or cut off clipping

25 For Q >> 1, the output frequency of LC oscillator is equal to resonant frequency.

A. True B. False

26. A Wien bridge oscillator uses Wien bridge for

A. tuning and phase shift B. tuning C. phase shift D. either tuning or phase shift

27. In a bistable multivibrator, commutating capacitors are used to

A. increase the base storage charge B. provide ac coupling C. increase the speed of response D. alter the frequency of the output

103

28. Which amplifier has a voltage gain of less than 1?

A. Common emitter B. Common collector C. Common base D. Both CB and CC

29. The main disadvantage of a JFET is

A. low gain-bandwidth product B. high noise level C. high cost D. low gain

30. With negative feedback the closed loop gain is always less than open loop gain.

A. True B. False

31. In CE amplifier circuit, voltage gain is directly proportional to

A. β B. collector supply voltage C. base resistance D. none of the above

32. Occasionally a discrete amplifier user RF chokes instead of collector resistors. Such amplifiers are inherently

A. low pass amplifiers B. high pass amplifiers C. band pass amplifiers D. none of the above

33. At the peak of negative half cycle in figure

A. diode A is forward biased and diode B is reverse biased B. both diodes are reverse biased C. both diodes are forward biased D. diode A is reverse biased and diode B is forward biased

34. In logarithmic amplifiers, output voltage is equal to

A. K.log10 (input voltage) B. K.loge (input voltage) C. input voltage

104

35. The input resistance R, of an ideal voltage amplifier is __________ and that of a current amplifier is __________ .

A. zero, zero B. infinite, infinite C. zero, infinite D. infinite, zero

36. If 1.5% of the output of an amplifier is feedback positively to the input, the minimum gain required of the amplifier for oscillations to occur, is

A. 16.6 B. 44.4 C. 66.6 D. 75

37. If a transistor is operating with both of its Junctions forward biased, but with the collector base forward biased, but with the collector base forward bias greater than the emitter-base forward bias, then it is operating in the

A. forward active mode B. reverse saturation mode C. reverse active mode D. forward saturation mode

38. Two 3ω speakers in series will have a total impedance of

A. 1 ω B. 3/2 ω C. 3 ω D. 6 ω

39. In a CE amplifier the ac signal is increased. Which of the following will not change?

A. Ac base voltage B. Ac collector voltage C. Ac emitter voltage D. Ac collector voltage and ac emitter voltage

40. The multivibrator circuit that has a typical application of converting sinusoidal input into a square wave output is

A. emitter coupled binary B. Schmitt trigger C. monoshot multivibrator D. free-running multivibrator

41. CC circuit is suitable for impedance matching.

A. True B. False

105

42. In the CE circuit shown in figure the slope of dc load line will be

A.

B.

C.

D.

43. The input resistance Ri of the amplifier shown in the figure

A. 30/40 kω

B. 100 kω C. 40 kω D. ∞

44. When narrow current pulses drive a high Q resonant circuit the voltage across the circuit looks like

A. narrow pulses B. half sine wave C. almost sine wave D. either (a) or (b)

45. Which of the following plot can be directly used to determine β?

A. VCE versus iC for constant IB B. VBE versus iB for constant VCE C. VCB versus iC for constant IB D. All of the above

106

46. Which of the following statement about JFET is correct?

A. In an N-channel JFET, the channel is the narrowest under zero gate bias condition B. In a JFET the gates are always forward biased C. In a JFET, gate-source cut off voltage is numerically equal to the pinch off voltage D. It is a voltage controlled device

47. The transconductance curve of a JFET is

A. a straight line B. parabolic C. hyperbolic D. inverted V-type

48. Low frequency response of amplifier is mainly limited by

A. input capacitor B. bypass capacitor C. output capacitor D. biasing capacitor

49. As compared to a bipolar transistor, a JFET is

A. highly sensitive to changes in input voltage B. more sensitive to changes in input voltage C. less sensitive to changes in input voltage D. equally sensitive to changes in input voltage

50. Which of the following number specification refers to FET with one gate?

A. 2N B. 3N C. 3Y D. 3X

Answer of Analog digital : CE amplifier, JEFT

1‐>1 , 2‐>1 , 3‐>1 , 4‐>3 , 5‐>2 , 6‐>1 , 7‐>3 , 8‐>4 , 9‐>1 , 10‐>1 , 11‐>2 , 12‐>3 , 13‐>2 ,

14‐>1 , 15‐>2 , 16‐>2 , 17‐>2 , 18‐>1 , 19‐>3 , 20‐>1 , 21‐>3 , 22‐>2 , 23‐>2 , 24‐>2 , 25‐>1

, 26‐>1 , 27‐>3 , 28‐>2 , 29‐>1 , 30‐>1 , 31‐>1 , 32‐>2 , 33‐>4 , 34‐>2 , 35‐>4 , 36‐>3 , 37‐

>3 , 38‐>2 , 39‐>3 , 40‐>2 , 41‐>1 , 42‐>1 , 43‐>2 , 44‐>3 , 45‐>1 , 46‐>3 , 47‐>2 , 48‐>2 ,

49‐>3 , 50‐>2

107

Analog Electronics

Section11:HartleyOscillator,Amplifiergain1. Oscillation of frequency in Hartley oscillator is

A.

B.

C.

D.

2. A transistor will operate in inverted region when

A. emitter junction is forward biased and collector junction is reverse biased B. emitter junction is reverse biased and collector junction is forward biased C. emitter junction as well as collector junction are forward biased D. emitter junction as well as collector junction are reverse biased

3. The advantage of using crystal oscillator is that it

A. requires low d.c. supply voltage B. works at high frequency C. gives high output voltage D. gives constant frequency of oscillations

4. A quiescent state of a transistor implies

A. zero bias B. no output C. no distortion D. no input signal

5. In the circuit shown in the figure, the approximate voltage at the transistor,

A. base and emitter respectively are -8 V and -7.3 V B. base and collector respectively are -8 V and -5 V C. Collector and emitter respectively are -5 V and -7.3 D. base, emitter and collector respectively are -8 V, 7.3 V and -5 V

108

6. A capacitor input filter relies on

A. average detection B. peak detection C. both (a) and (b) D. neither (a) nor (b)

7. The IF amplifier in a superheterodyne receiver is

A. single-stage single-timed amplifier B. two stage of single tuned amplifier C. double tuned amplifier D. class-C amplifier

8. If input ac is 10 Vrms, then maximum voltage that will appear across the diode of a half wave rectifier with a capacitor I/P filter will be

A. 10 V B. 14 V C. 20 V D. 28 V

9. A dc amplifier can operate

A. at zero frequency B. only at low frequency C. only at high frequencies D. both at low and high frequencies

10. The approximate value of input impedance of CE amplifier with emitter resistance RE is given by

A. hie + Ai RE B. hie + (1 + hfe) RE C. hie D. (1 + hfe) RE

11. Which of the following couplings may cause unwanted clamping?

A. Resistive B. Inductive C. Capacitive D. Both (a) or (b)

12. Assertion (A): In a circuit using FET, gate is approximately at dc ground

Reason (R): Self bias stabilizes the quiescent operating point against changes in JFET parameters


109

13. Which of the following contributes to harmonics distortion in amplifiers?

A. Positive feedback B. Presence of noise C. Defective active device D. Non-linearity in active device

14. The name field effect is related to the __________ layers of a JFET.

A. depletion B. drain C. source D. gate

15. An amplifier signal is made up of just two frequencies 1000 Hz. The output signal consists of 500 Hz and 25000 Hz frequencies. This may be attributed to

A. harmonic distortion B. intermodulation distortion C. both (a) and (b) D. none of the above

16. Examine the circuit of figure and the following statements

Vs is more than the zener breakdown voltage. IL = I1 - I2. Rs is less than zener nominal resistance. Which of the above statements are correct?

A. 1, 2, 3 B. 1, 2 C. 1 only D. 2 and 3

17. Which of the following are synonymous?

A. MOSFET and IGEFT B. FET and JFET C. JFET and MOSFET D. P-N-P and N-P-N

18. In a tuned class C power amplifier the quiescent value of collector to emitter voltage is equal to (VCC denotes collector battery voltage)

A. VCC B. 0.5 VCC C. 0.25 VCC D. either (b) or (c)

110

19. A voltage doubler circuit uses

A. two diodes B. two capacitors C. two diodes and two capacitors D. none of the above

20. For an amplifier, the coupling method which gives the highest gain in

A. impedance coupling B. transformer coupling C. capacitance coupling D. resistance coupling

21. To obtain very high input and O/P impedance in a feedback amplifier, the type of feedback utilized

A. voltage series B. current series C. voltage shunt D. current shunt

22. Which amplifier will be preferred for highest gain?

A. Darlington's pair B. Single stage amplifier C. Cascade amplifier D. Depends on the circuitry

23. The conversion or collector circuit efficiency is a measure

A. how successfully the active device converts D.C. power to A.C. signal power B. how much distortion in output is reduced with respect to input C. how successfully the active device converts A.C. power to D.C. signal power D. none of the above

24. Oscillator with best frequency stability is

A. Crystal oscillator B. Phase shift oscillator C. Clapp oscillator D. Hartley oscillator

25. The emitter follower steps up the impedance by a factor of

A. a B. β C. a β D. a/β

26. A transistor amplifier is operating in class A mode. If a transformer is connected for impedance matching, the efficiency will

A. increase B. decrease C. not be affected D. increase or decrease

111

27. Thermal runaway will take place if the quiescent point is such that

A. VCE >1/2 VCC B. VCE < VCC C. VCE < 2VCC D. VCE <1/2 VCC

28. A Clapp's oscillator is

A. a modified Hartley oscillator B. a modified Colpitt's oscillator C. a modified RC oscillator D. none of the above

29. Volt equivalent temperature in a PN Junction diode is

A.

B.

C.

30. Primary advantage of a crystal oscillator is that

A. it can oscillate at any frequency B. it gives a high O/P voltage C. its frequency of oscillation remains almost constant D. it operates on a very low dc supply voltage

31. In applications where __________ input resistance is needed, the JFET is preferred to the bipolar transistor.

A. zero B. very low C. low D. high

32. Assertion (A): In a common source amplifier with source terminal at ac ground the voltage gain is about gm rd

Reason (R): A common source amplifier is a source follower circuit


33. RECTIFIER : OSCILLATOR ::

A. Capacitance : Inductance B. Series resonance : Parallel resonance C. DC : AC D. Regulation : Efficiency

112

34. In figure the collector to emitter breakdown voltage of the transistor (βVCEO) should be

A. more than VCC B. more than 0.5 VCC C. more than VCC + E D. more than 2 VCC

35. Cross-over distortion behaviour is a characteristic of

A. class A output stage B. class B output stage C. class AB output stage D. common base output stage

36. In order to protect a MOSFET against damage from any stray voltage at the gate

A. grounding rings are provided B. terminals are shorted C. source terminal is earthed during transit D. none of these

37. The pinch-off voltage is the drain voltage on the shorted gate drain curve above which the drain current becomes

A. almost negligible B. very high C. almost constant D. highly variable

38. In a P-N-P transistor, with normal bias, the emitter junction

A. is always reverse biased B. offers very high resistance C. offers a low resistance D. remains open

39. Which of the amplifier circuits using junction transistors has the best gain?

A. Common emitter B. Common base C. Common collector D. All above has the same gain

113

40. An ideal op-amp can amplify dc signals

A. True B. False

41. Which of the following plot can be used to show the input volt-ampere characteristics of a common-emitter configuration?

A. VBE versus iB for constant values of VCE B. VCE versus iC for constant values of IB C. VCE versus iC for constant values of IE D. None of the above

42. A transconductance amplifier has

A. high input impedance and low output impedance B. low input impedance and high output impedance C. high input and output impedance D. low input and output impedance

43. In each of circuits below, indicate which diode is conducting?

A. Figure A B. Figure B C. Figure C D. All the three

44. A transistor may fail due to

A. open weld at the wire leads to the semi-conductor B. short circuit caused by momentary overloads C. overheating due to circuit failures D. any of the above

45. The thermal resistance of a BJT is about

A. 100° C/W B. 200° C/W C. 20° C/W D. 2° C/W

114

46. Figure represents

A. Adder B. Multiplier C. Subtractor D. Log Amplifier

47. Consider the following statements : The lower cut off frequencies of an RC coupled amplifier depend on

input and output coupling capacitor emitter by pass capacitors junction capacitances Which of the above are correct?

A. 1 only B. 2 only C. 1 and 2 D. 2 and 3

48. The Darlington pair consists of the following two stages

A. CE and CC B. both CE C. both CC D. CE and CB

49. The signal input to a given amplifier is made up of 100 mω signal power and 1 mω noise power. The amplifier contributes an additional 100 mω of noise and has a power gain of 20 dB. The output signal-to-noise ratio is

A. 100 B. 50 C. 10 D. 5

50. If input frequency is 50 Hz, the frequency of output wave in a half wave diode rectifier circuit is

A. 25 Hz B. 50 Hz C. 100 Hz D. 200 Hz

115

Answer of Analog digital : Hartley Oscillator, Amplifier gain

1‐>2 , 2‐>2 , 3‐>4 , 4‐>3 , 5‐>4 , 6‐>2 , 7‐>2 , 8‐>2 , 9‐>1 , 10‐>3 , 11‐>3 , 12‐>2 , 13‐>4 ,

14‐>1 , 15‐>2 , 16‐>2 , 17‐>1 , 18‐>1 , 19‐>3 , 20‐>2 , 21‐>2 , 22‐>3 , 23‐>1 , 24‐>1 , 25‐>2

, 26‐>1 , 27‐>1 , 28‐>2 , 29‐>1 , 30‐>3 , 31‐>4 , 32‐>3 , 33‐>4 , 34‐>2 , 35‐>2 , 36‐>3 , 37‐

>3 , 38‐>3 , 39‐>1 , 40‐>1 , 41‐>1 , 42‐>3 , 43‐>4 , 44‐>4 , 45‐>2 , 46‐>3 , 47‐>1 , 48‐>3 ,

49‐>2 , 50‐>2

116

Analog Electronics

Section12:Aperturecircuit,Clipper1. If Rs is the sources resistance, the O/P resistance of an emitter follower using the simplified hybrid model would be

A.

B.

C.

D.

2. A generator with an internal resistance of 600 ω drives an amplifier whose input resistance is 400 ω. The generator's open circuit voltages is 1 mV; the amplifier develops 100mV across an 8kω load. The current amplification is

A. 2.5 B. 12.5 C. 25 D. 125

3. The oscillator shown in figure is a

A. Colpitt's oscillator B. Hartley oscillator C. Tuned emitter oscillator D. Clapp oscillator

117

4. In which configuration does output ac voltage appear between emitter and ground?

A. CE B. CB C. CC D. Both CE and CB

5. In a class C operation

A. VCC is much larger than VCE(sat) B. VCC is much smaller than VCE(sat) C. VCC and VCE(sat) are nearly equal D. none of the above

6. In a resistance loaded amplifier, the gain decreases at high frequencies because

A. decreasing reactance of the stray CT B. increasing reactance of the stray CT C. increasing reactance of CT D. decreasing reactance of CT

7. The emitter bias largely depends on

A. gain B. signal input C. IE D. none of the above

8. For a good voltage amplifier, its input impedance should be

A. low as compared to the resistance of the source B. high as compared to the resistance of the source C. always inductive D. always capacitive

9. A transistor in CE mode is in saturation region. Then the collector is almost at

A. ground potential B. a potential equal to VCC C. a potential equal to 0.5 VCC D. a potential equal to 2 VCC

10. Most of the transistor data sheets specify the power rating for an ambient temperature of

A. 10°C B. 25°C C. 50°C D. 75°C

118

11. For an amplifier the input output signals are shown in figure. The class of amplifier is

A. A B. AB C. B D. C

12. The main use of JFET with a

A. frequency mixer B. source follower C. voltage doubler D. trigger

13. In a shunt-shunt negative feedback amplifier, as compared to the basic amplifier

A. both input and output impedances, decrease B. input impedance decreases but output impedance increase C. I/P impedance increases but O/P impedance decreases D. both input and O/P impedance increases

14. A pulse transformer uses

A. ferrite core B. air core C. iron core D. copper core

15. The early effect in BJT is caused by

A. fast turn on B. fast turn off C. large collector base reverse bias D. large emitter base forward bias

16. A Darlington pair is used for

A. low distortion B. high frequency range C. high power gain D. high current gain

17. A Hartley oscillator uses

A. a tapped capacitor B. a tapped inductor C. a tapped inductor for inductive feedback D. none of the above

119

18. In figure the voltage gain is

A. B. re

C.

D.

19. The circuit in figure is

A. positive clamper B. negative clamper C. positive peak clipper D. negative peak clipper

20. In rectifiers the use of RC filters is recommended when

A. load current is high B. load current is small C. load current is neither high nor small D. either (a) or (c)

21. The static characteristic of an adequately forward biased p-n junction is a straight line if the plot is of

A. log I vs log V B. log I vs V C. I vs log V D. I vs V

120

22. Assertion (A): A dc stabilizer has constant output voltage irrespective of variations in input voltage and load current

Reason (R): A dc series regulator uses a zener diode across the load to stabilize the output voltage.


23. The main drawback in the performance of shunt peaked wide band amplifier is

A. two low gain at low frequency B. poor phase response C. reduce frequency at middle frequency D. that the maximum gain of the stage is small

24. The noise figure is

A. 3 dB B. 6 dB C. 6.6 dB D. 12 dB

25. In a CE amplifier circuit

A. Q point must lie on both dc and ac load lines B. Q point lies on dc load line C. Q point lies on ac load line D. Q point lies may or may not lie on both dc and ac load lines

26. In the self biasing scheme (RF across collector to base) of BJT, S1 tends to unity by __________ RC is the collector load Resistance.

A. increasing RF B. decreasing RF C. decreasing RF and increasing RC D. increasing RF and decreasing RC

27. Aperture circuit produces __________ in sample hold circuit.

A. the total sampling time B. delay between the instance at which hold command is initiated and the instance at which O/P starts tracking I/P C. the time taken by O/P to settle within the specified 1% error band, that of the I/P D. time required by holding capacitor to reach upto the level close to input

121

28. The frequency response of an ideal tuned amplifier should be as represented in figure by

A. A B. B C. C D. D

29. One of the major applications of JFET is in

A. switching B. constant current-source C. constant voltage-source D. electron flow regulation

30. Which of the following circuits can operate class AB for audio power output?

A. Emitter follower B. Push pull C. Cascade D. Darlington pair

122

31. In figure vi is a sinusoidal wave. Which of the following best describes the output v0?

A.

B.

C.

D.

32. In common base amplifier the current gain is less than one, but the voltage gain may be anywhere from

A. 0.5 to 1 B. 1 to 5 C. 5 to 10 D. 50 to 2000

33. Transformer coupling in transistor amplifier circuits provides high efficiency, because

A. d.c. resistance is low B. collector voltage is stepped up C. flux linkages are incomplete D. all of the above

34. The coupling capacitor mainly affects

A. bandwidth B. lower cut-off frequency C. higher cut-off frequency D. both lower as well as higher cut-off frequency

123

35. A 1 ms pulse can be stretched to 1 sec pulse by using

A. an astable multivibrator B. a monostable multivibrator C. a bistable multivibrator D. a Schmitt trigger circuit

36. Gain stability in an oscillator can bs achieved by

A. providing negative feedback B. providing positive feedback C. using low Q circuits D. controlling the gain

37. A D.C. amplifier amplify

A. D.C. only B. A.C. only C. both A.C. and D.C. D. none of the above.

38. In op-amp integrating amplifier the input is feed to

A. inverting input B. non-inverting input C. both inverting and non-inverting input D. either inverting or non-inverting input

39. At high frequencies the output circuit of transistor amplifier reduces to

A. a lead network B. a lag network C. either (a) or (b) D. neither (a) nor (b)

40. Two identical FETs each having parameters gm and rd are connected is parallel. The composite FET has parameters

A. 0.5 gm and 2 rd B. 0.5 gm and 0.5 rd C. 2 gm and 2 rd D. 2 gm and 0.5 rd

41. A clipper

A. adds a dc component to the input signal B. removes signal voltages above or below a specified value C. both (a) and (b) D. either (a) or (b)

42. In a rectifier circuit the filter capacitance is increased. Then the ripple will

A. increase B. decrease C. remain the same D. either (a) or (b)

124

43. A CE amplifier is the most common BJT amplifier.

A. True B. False

44. Figure represents a

A. JFET shunt switching circuit B. JFET series switching circuit C. JFET analog switch D. multiplexing

45. If f is more than funity the gain of op-amp becomes less than 1.

A. True B. False

46. In a push pull circuit the two transistors are

A. both pnp B. both npn C. one pnp and other npn D. either (a) or (b)

47. Figure represents

A. Integrator B. Differentiator C. High Pass Filter D. Band Pass Filter

125

48. In a N-P-N transistor the function of the emitter is

A. to emit or inject holes into the collector B. to emit or inject electrons into the collector C. to emit or inject electrons into the base D. to emit or inject holes into the base

49. The semi-conductor type 2 N 34 indicates

A. a n-channel MOSFET B. a JFET C. a diode with two electrodes D. a diode with three electrodes

50. In a P-N-P transistor, with normal bias

A. the collector junction has negligible resistance B. only holes cross the collector junction C. the collector-base junction is reverse biased and the emitter base junction is forward biased D. only majority carriers cross the collector junction

Answer of Analog digital : Aperture circuit, Clipper

1‐>1 , 2‐>2 , 3‐>1 , 4‐>3 , 5‐>1 , 6‐>1 , 7‐>3 , 8‐>2 , 9‐>1 , 10‐>2 , 11‐>4 , 12‐>2 , 13‐>2 ,

14‐>1 , 15‐>3 , 16‐>4 , 17‐>3 , 18‐>3 , 19‐>1 , 20‐>2 , 21‐>2 , 22‐>2 , 23‐>2 , 24‐>1 , 25‐>1

, 26‐>3 , 27‐>2 , 28‐>3 , 29‐>1 , 30‐>4 , 31‐>2 , 32‐>4 , 33‐>1 , 34‐>2 , 35‐>2 , 36‐>4 , 37‐

>1 , 38‐>1 , 39‐>2 , 40‐>4 , 41‐>2 , 42‐>2 , 43‐>1 , 44‐>2 , 45‐>1 , 46‐>3 , 47‐>1 , 48‐>3 ,

49‐>3 , 50‐>3

126

Analog Electronics

Section13:RippleFactor,DelayEqulazier

1. According to Barkhausen criteria in order to sustain the oscillations

A. loop gain of the circuit must be negligible B. loop gain of the circuit must be equal to unity C. the phase shift around the circuit must be 180° D. none of the above

2. A transistor is said to be in a quiescent state when

A. the amplitude of input and output signal is equal B. the phase of input and output signal is identical C. no signal is applied to the input D. the transistor is unbiased

3. The source of the harmonic distortion in a RC coupled transistor amplifier is usually

A. power supply B. capacitor C. R-C circuit D. transistor

4. The input impedance of a non-inverting amplifier is very low.

A. True B. False

5. A class C amplifier uses

A. high Q tuned circuit B. low Q tuned circuit C. untuned circuit D. either (b) or (c)

6. In figure

A. the collector currents of T1 and T2 are equal B. the collector current of T1 is more than that of T2 C. the collector current of T1 is double that of T2 D. the collector currents of T2 is more than that of T1

127

7. In a Hartley oscillator the condition for sustained oscillations is If there exists mutual inductance M between coils L1 and L2, then the above condition will get modified as hfe

A.

B.

C.

D.

8. For an I/p of Vs = 5 sin ωt (assuming ideal diode), circuit shown in the figure will behave as a

A. clipper, sine wave clipped at -2 V B. clamper, sine wave clamped at -2 V C. clamper, sine wave clamped at 0 volts D. clipper, sine wave clipped at 2 V

9. In an op-amp a common mode signal is applied to

A. inverting terminal B. non-inverting terminal C. both terminals D. one or both the terminals

10. Wide banding technique is employed in the

A. video amplifier of a TV receiver B. IF amplifier of an FM receiver C. RF amplifier of an AM receiver D. input section of a communication receiver

128

11. In order to obtain triangular pulses at the output of the circuit in the figure, the input should be.

A. grounded B. a square wave C. Triangular wave D. Trigger

12. Which one of the following devices is not used as the controller in a stabilizer?

A. DIAC B. TRIAC C. SCR D. Power transistor

13. In a combination limiter with sinusoidal input voltage the output wave can be nearly square.

A. True B. False

14. A Hartley oscillator uses

A. a tapped inductor B. a tapped capacitor C. both (a) and (b) D. neither (a) nor (b)

15. A bipolar transistor is a __________ controlled devices whereas a FET is a __________ controlled devices.

A. current, voltage B. current, current C. voltage, current D. voltage, voltage

129

16. The oscillator shown in figure is a

A. Clapp oscillator B. R-C Phase shift oscillator C. Hartley oscillator D. Colpitt's oscillator

17. Which of the following are difficult to be fabricated in a monolithic IC?

A. Inductors B. Large capacitors C. Small capacitors D. Both (a) and (b)

18. The properties of FETs resemble closely to

A. UJT B. current transformer C. thyristor D. thermionic valves

19. A FET has

A. very high input resistance B. very low input resistance C. high connection emitter junction D. forward biased PN junction

20. A feedback network to be used with an amplifier to provide oscillation is tested and found to give an output of 0.124 V with a 0.5 V input. What will be the effect on output if the amplifier's gain is twice that required by the Barkhausen criterion?

A. Linear oscillations B. Non-linear oscillations C. Damped oscillations D. No oscillations

130

21. Which of the following can be used to isolate a low impedance from a high impedance source?

A. Emitter follower B. p filter C. Darlington pair D. Any of the above

22. High frequency oscillations can be caused by

A. electric coupling B. magnetic coupling C. ground loop D. all of the above

23. A delay equalizer is a

A. low pass filter B. band pass filter C. all pass filter D. high pass filter

24. Equal amplitude ac signals are given as inputs to both inverting and given as inputs to both inverting and non-inverting terminals of an op-amp. The output will be zero when the phase difference between inputs is

A. 0° B. 90° C. 180° D. 270°

25. A two stage amplifier has an upper cutoff frequency of 2 MHz and a lower cutoff frequency of 2 MHz and a lower cut off frequency of 30 Hz. If both stages are similar, their individual upper and lower cut off frequencies respectively are

A. 4 MHz and 60 MHz B. 3 MHz and 20 Hz C. 3 MHz and 60 Hz D. 4 MHz and 20 Hz

26. Which distortion is least objectionable in case of audio amplifiers?

A. Phase distortion B. Frequency distortion C. Harmonic distortion D. Inter-modulation distortion

27. A three-section RC phase shift oscillator has R = 10K ohms and C = 0.001 μF. If the oscillator is to be made variable using the same value of R, what should be the value of capacitor to obtain a frequency if 1 kHz?

A. 636 pF B. 180 pF C. 65 pF D. 30 pF

131

28. A silicon PN junction diode under reverse bias has depletion region of width 10 μm. The relative permittivity of silicon, εr = 11.7 and the permittivity of free space ε0 = 8.85 x 10-12 F/m. The depletion capacitance of the diode per square meter is

A. 100 μF B. 10 μF C. 1 μF D. 20 μF


A. rectifier B. voltage to frequency converter C. frequency to voltage converter D. logarithmic amplifier

30. A limiter circuit can be built using a diode and resistance.

A. True B. False

31. The ripple factor of a full wave rectifier is about 0.5.

A. True B. False

32. FET can used in

A. buffer amplifier circuits B. cascade amplifier circuits C. digital circuits D. all of the above

33. RC oscillator can be used upto

A. 1 kHz B. 10 kHz C. 50 kHz D. 100 kHz

132

34. Assertion (A): A Darlington amplifier has very low output impedance

Reason (R): The circuit has a low resistance RE between emitter and ground


35. A Wien bridge oscillator uses

A. negative feedback B. positive feedback C. both negative and positive feedback D. none of the above

36. In the above case, what will be the value of capacitor to obtain 100 kHz frequency?

A. 0.0065 pF B. 0.0130 pF C. 0.0260 pF D. 0.520 pF

37. The disadvantage of transformer coupling in amplifier is

A. cost of transformer at audio frequencies B. size of transformer at audio frequencies C. size of transformer at radio frequencies D. cost and size of transformer at audio frequencies

38. Which of the following op-amp circuits has zero resistance in the feedback path?

A. Inverting amplifier B. Summing amplifier C. Source follower D. Integrating amplifier


A. CE amplifier B. CB amplifier C. Constant voltage source D. Constant current source

133

40. Assertion (A): The maximum efficiency of a class B push pull amplifier is 78.5%

Reason (R): A current mirror uses a compensating diode in parallel with the emitter diode


41. In saturation region JFET acts like a

A. bipolar device B. short circuit C. switch D. resistance

42. In a single stage differential amplifier, the output offset voltage is mainly dependent on the mismatch of

A. VBE, IB and β B. VBE and IB C. IB and β D. VBE and β

43. In a N-P-N transistor of the emitter junction is reverse biased and collector junction is also reversed biased, the transistor will operate in

A. active region B. saturation region C. cut-off region D. inverted region

44. Each of two cascaded stages has a voltage gain of 30. The overall gain is

A. 3 B. 9 C. 30 D. 900

45. Figure shows current pulses of a class C power amplifier. The fundamental frequency of these pulses is

A. 100 kHz B. 1000 kHz C. 10 kHz D. 1 kHz

134

46. In an LC filter, the ripple factor,

A. increases with load current B. increases with load resistance C. remains constant with the load current D. has the lowest value

47. The input to negative clamper has a peak value of Vp. Then in the output the positive and negative peaks are nearly

A. 0 and -2 V respectively B. Vp and -Vp respectively C. 2 Vp and 0 respectively D. none of the above

48. In a common Emitter BJT amplifier, the maximum usable supply voltage is limited by

A. avalanche breakdown of Base emitter junction B. collector to Base Breakdown voltage with emitter open (βVCBO) C. collector Emitter Breakdown voltage with base open (βVCBO) D. zener breakdown voltage of the emitter base Junction

49. Two transistors have same value of a but different gain (G) bandwidth (B) product. The transistors have similar geometry. However one of them is germanium and the other is silicon. The transistor with lower GB product

A. is germanium B. is silicon C. may be either of two D. cannot be identified on the basis of above data

50. A cascade amplifier stage is equivalent to

A. common emitter stage followed by a common base stage B. common base stage followed by an emitter follower C. an emitter follower stage followed by a common base stage D. a common base stage followed by a common emitter stage

Answer of Analog digital : Ripple Factor, Delay Equlazier

1‐>3 , 2‐>3 , 3‐>4 , 4‐>2 , 5‐>1 , 6‐>1 , 7‐>3 , 8‐>4 , 9‐>3 , 10‐>1 , 11‐>1 , 12‐>1 , 13‐>1 ,

14‐>1 , 15‐>1 , 16‐>1 , 17‐>4 , 18‐>3 , 19‐>1 , 20‐>4 , 21‐>3 , 22‐>4 , 23‐>2 , 24‐>1 , 25‐>2

, 26‐>1 , 27‐>3 , 28‐>2 , 29‐>4 , 30‐>1 , 31‐>1 , 32‐>1 , 33‐>2 , 34‐>3 , 35‐>3 , 36‐>1 , 37‐

>4 , 38‐>3 , 39‐>3 , 40‐>2 , 41‐>4 , 42‐>2 , 43‐>3 , 44‐>4 , 45‐>1 , 46‐>4 , 47‐>1 , 48‐>4 ,

49‐>2 , 50‐>1

135

Analog Electronics

Section14:TRIAC,PowerAmpliflier

1. Which of the following uses a capacitor in the feedback path?

A. Active low pass filter B. Active high pass filter C. Both (a) or (b) D. Neither (a) nor (b)

2. A push pull amplifier balance out

A. odd harmonics B. even harmonics C. both odd as well as even harmonics D. neither odd nor even harmonics

3. In figure VBE = 0.7 V. If base current required to saturate the transistor is 0.1 mA, Vi =

A. 5 V B. 5.7 V C. 10 V D. 10.7 V

4. Figure shows a zener circuit and characteristic of the zener used. If R2 is the lowest load resistance, then for proper voltage regulation R1 must be

A. more than

B. more than

C. less than

D. less than

136

5. The units of q/kt are

A. V B. V-1 C. J D. J/K

6. Assertion (A): In a differential amplifier the current through common emitter resistor is called tail current

Reason (R): CMRR of an op-amp indicates how a differential signal amplified


7. In a bipolar transistor at room temperature if the emitter current is doubled the voltage across its base emitter junction

A. doubles B. halves C. increase by about 20 mV D. decrease by about 20 mV

8. Logarithmic amplifiers are used in

A. adders B. dividers C. multipliers D. all of the above

9. A BJT amplifier has a power gain of 0.5 from source to base. The power gain in dB is

A. -0.3 dB B. -3 dB C. -6 dB D. -10 dB


A. JFET shunt switching circuit B. JFET series switching circuit C. JFET analog switch D. multiplexing

137

11. In a half wave rectifier, Vrms is

A.

B.

C.

12. For a transistor the normal collector voltage is 12 V. If actually it is found to be + 28 V, the trouble could be

A. RL is open B. RE is open C. CE is shorted D. CE is open

13. The voltage gain of which transistor configuration is less than unity?

A. CB B. CE C. CC D. None

14. A TRIAC is a semiconductor device which acts as a

A. 2 terminal unidirectional switch B. 2 terminal bidirectional switch C. 3 terminal bidirectional switch D. 4 terminal multidirectional switch

15. CE mode input V-I characteristic can be shown by a plot of

A. VBE versus iB for constant values of VCE B. VCB versus iC for constant values of IE C. VCE versus iE for constant values of VEB D. VCE versus iE for constant values of VCE

16. Negative feedback lowers the cut off frequency and increase the upper cut off frequency of amplifier.

A. True B. False

17. Negative feedback is used in audio amplifiers to

A. operate class C B. reduce distortion C. increase distortion D. increase gain

18. A complementary symmetry amplifier has

A. 1 P-N-P and 1 N-P-N transistor B. 2 P-N-P transistor C. 2 N-P-N transistor D. 2 P-channel FETs

138

19. A Darlington pair has β = 300. If RE = 1 kω and RL = 100 ω, the input impedance at the base is approximately

A. 300 k ohm B. 3 k ohm C. 100 k ohm D. 30 k ohm

20. Zero bias works only with

A. D MOSFETs B. E MOSFETs C. both D and E MOSFETs D. neither D nor E MOSFETs

21. Linear transistor circuits always operate in

A. saturation region B. cut off region C. active region D. passive region

22. As per miller theorem the circuit of figure (1) can be replaced by that in figure (2) If V1/V2= K, then Y1 and Y2 are equal to

A. Y(1 - K) each

B. each

C. Y1 = Y(1 - K) and Y2 =

D. Y1 = and Y2 = (1 - K)

23. Assertion (A): In class A amplifier the distortion is minimum

Reason (R): In class A amplifier collector current exists for 360° of input cycle


139

24. In a Darlington pair

A. the emitter of first transistor drives the base of the second B. the base of the first transistor drives the emitter of the second C. emitters of the two transistors are connected through a resistor D. none of the above

25. In an inverting amplifier using op-amp the current input to the inverting terminal

A. is equal to the current through feedback resistance B. is less than the current through feedback resistance C. is more than the current through feedback resistance D. may be equal to, less or more than current through feedback resistance

26. Which one of the following power amplifier has the maximum efficiency?

A. Class A B. Class B C. Class AB D. Class C

27. The common emitter short circuit current gain β of a transistor

A. is a monotonically increasing function of the collector current Ic B. is a monotonically decreasing function of Ic C. increasing with Ic, for low Ic, reaches a maximum and then decreases with further increase in Ic D. is not a function of Ic

28. The Clapp oscillator shown in figure will operate at

A. 4.6 kHz B. 46 kHz C. 460 kHz D. 4600 kHz

29. Which circuit is called emitter follower?

A. CC B. CE C. CB D. Both (a) and (b)

140

30. Assertion (A): Manufacturer's quote h parameters of transistor

Reason (R): h parameters of a transistor are easiest to measure


31. Wien bridge uses

A. lead network B. lag network C. lead-lag network D. Both (a) and (b)

32. In a single-stage RC coupled common emitter amplifier, the phase shift at the lower 3 dB frequency is

A. zero B. 135° C. 180° D. 225°

33. Figure shows small signal model of CB amplifier circuit. Then I and R are respectively equal to

A. a ie and re

C. a ie and re (a - 1) D. (a - 1) ie and re

34. Which of the following compensation method in amplifier can be used to reduce the bandwidth?

A. Pole-zero compensation B. Dominant pole compensation C. Lead compensation D. Any of the above

35. In a CE transistor amplifier, when collector-emitter voltage increases

A. the instantaneous operating point moves up the load line B. the instantaneous operating point moves down the line C. load current increases D. none of the above

141

36. The current ICBO

A. increases with increases in temperature B. is normally greater for silicon transistor than germanium transistors C. mainly depends on the emitter base junction bias D. depends largely on the emitter doping

37. In CC configuration, the output signals has approximately

A. the same amplitude and phase B. opposite amplitude and phase C. same amplitude but opposite phase D. none of the above

38. The P-type substrate in a conventional pn Junction isolated integrated circuits should be connected to

A. any where B. a dc ground potential C. the most positive potential available in the circuit D. the most negative potential available in the circuit

39. If the thermal resistance of a transistor is lower it means

A. higher junction temperature B. lower junction temperature C. higher or lower junction temperature depending on circuit conditions D. higher or lower junction temperature depending on transistor

40. The PIV of a bridge rectifier is less than that of full wave rectifier with centre tapped transformer.

A. True B. False

41. Barkhausen criterion is 1 + Avβ = 0.

A. True B. False

42. Quartz crystal has

A. very small Q B. small Q C. very high Q D. Q less than 1

43. In graphical analysis of BJT amplifier the slope of ac line is more than that of dc load line.

A. True B. False

44. Which one of the following power amplifier has the maximum efficiency?

A. Class A B. Class B C. Class AB D. Class C

142

45. Assertion (A): In a push pull circuit each transistor stays in the active region for one half cycle

Reason (R): A push pull amplifier has low distortion


46. Which of the following statement is correct?

A. A FET is a current controlled device B. A BJT is always reverse biased C. The semi-conductor material of the gate in an N-channel JFET is p-type D. JFET has higher input impedance than MOSFET

47. In figure, VC is approximately equal to

A. 2 V B. 4.6 V C. 8 V D. 7.6 V

48. A rectifier circuit has load resistance R. It uses a capacitance filter having capacitance C. For low ripple in the output

A. RC should be 1 B. RC should be low C. RC should be high D. RC should be neither low nor high

143

49. In a biased JFET (Figure) the shape of the channel is as shown because

A. it is the property of material used B. the drain end is more reverse biased than source end C. drain end is more forward biased than source end D. impurity profile changes with distance

50. n-channel MOS is

A. slower than p-channel MOS B. faster than p-channel MOS C. same as p-channel MOS D. none of these

Answer of Analog digital : TRIAC, Power Ampliflier

1‐>1 , 2‐>1 , 3‐>2 , 4‐>3 , 5‐>2 , 6‐>3 , 7‐>2 , 8‐>2 , 9‐>2 , 10‐>1 , 11‐>1 , 12‐>2 , 13‐>3 ,

14‐>3 , 15‐>1 , 16‐>1 , 17‐>2 , 18‐>1 , 19‐>2 , 20‐>1 , 21‐>3 , 22‐>3 , 23‐>1 , 24‐>1 , 25‐>1

, 26‐>1 , 27‐>3 , 28‐>3 , 29‐>1 , 30‐>1 , 31‐>3 , 32‐>2 , 33‐>1 , 34‐>2 , 35‐>1 , 36‐>1 , 37‐

>1 , 38‐>3 , 39‐>2 , 40‐>1 , 41‐>1 , 42‐>3 , 43‐>1 , 44‐>4 , 45‐>1 , 46‐>3 , 47‐>3 , 48‐>3 ,

49‐>2 , 50‐>2

144

Analog Electronics

Section15:CMOS,DarlingtonPair1.The circuit of figure is

A. clipper, sine wave clipped at - 2 V B. clamper C. clamper, sine wave clamped at zero V D. clipper, sine wave clipped at + 2 V

2. The collector voltage VC of the circuit shown in the given figure aside is approximately

A. 2 V B. 4.6 V C. 8 V D. 8.6 V

3. Which of the following best represents the output impedance of an actual op-amp?

A. 10 ohm B. 100 ohm C. 10 k ohm D. 100 k ohm

4. The linear transistor circuits always operate in the

A. saturation B. cut off C. active D. inactive

145

5. In figure, the function of resistor R is

A. to reduce ripples in the output B. to improve voltage regulation C. to limit the surge current D. either (a) or (c)

6. In the circuit shown in the figure

A. only red will glow B. only green will glow C. both red and green will glow D. none will glow

7. A class B amplifier

is biased just at cutoff has a high theoretical efficiency of 78.5% because its quiescent current is low is biased at midpoint of load line Of the above statements

A. 2 and 3 are correct B. 1 alone is correct C. 1 and 2 are correct D. 2 alone is correct

8. A generator with an internal resistance of 600 ω drives an amplifier whose input resistance is 400 ω. The generator's open circuit voltages is 1 mV; the amplifier develops 100mV across an 8kω load. The voltage multiplication is

146

A. 25 B. 50 C. 125 D. 250

9. A generator with an internal resistance of 600 ω drives an amplifier whose input resistance is 400 ω. The generator's open circuit voltages is 1 mV; the amplifier develops 100mV across an 8kω load. The power gain is

A. 125 B. 250 C. 1125 D. 3125

10. The phase angle of a lag circuit is

A. between 0 and -90° B. between 0 and +90° C. 90° D. more than 90°

11. In every practical oscillator, the loop gain is slightly larger than unity and the amplitude of the oscillations is limited by the

A. magnitude of the loop gain B. onset if non-linearity C. magnitude of gain of the amplifier D. feedback transmission factor

12. The symbol shown in figure represents a

A. P-channel MOSFET B. UJT with N-type base C. N-channel DEMOSFET with internal zener protection D. P-channel DEMOSFET with internal zener protection

13. In CE amplifier

A. input and output are in phase B. phase difference between input and output is 30° to 90° C. phase difference between input and output is 60° to 120° D. output is inverted with respect to its input voltage

14. The transformer cores operating at microwave frequency ranges are generally made up of

A. silicon steel B. ferrites C. albino D. super alloy

147

15. In an amplifier circuit the emitter is at ac ground potential in a

A. CB circuit B. CC circuit C. CE circuit D. both CB and CE circuit

16. In the graphical analysis of CE amplifier circuit, the intersection of base current and dc load line is called

A. saturation point B. cut off point C. Q point D. operating point

17. Emitter follower is in which of following configuration.

A. common Base B. common Emitter C. common collector D. common Base or common Emitter

18. The phase angle of lead circuit is

A. between 0 and -90° B. between 0 and +90° C. 90° D. more than 90°

19. Stability factor for S is given by for a fixed bias

A. 1 + β B. 1 - β C. 1/β D. β - 1

20. Which junction transistor is preferred for high input and low output impedances?

A. Common emitter B. Common base C. Common collector D. Any of the above

21. In CE circuit the parameter f12 is very small.

A. True B. False

22. The approximate value of input impedance of a common emitter amplifier with emitter resistance Re is given by

A. hie + AI Re B. hie + (i + hfe) Re C. hie D. (1 + hfe) Re

148

23. Sweep voltage generators, sweep current generators, multivibrators and blocking oscillators can be combined as

A. negative resistance oscillators B. tuned base tuned collector oscillators C. relaxation oscillators D. L-C tuned oscillators

24. Which of the following h parameters is an admittance?

A. hie B. hre C. hfe D. hoe

25. The voltage gains of an amplifier without feedback and with negative feedback respectively are 100 and 20. The percentage of negative feedback would be. A. 40% B. 5% C. 20% D. 80%

26. Saturation region of a JFET is also known as

A. source region B. analog region C. pinch off region D. ohmic region

27. Which of the following statement is false? A. The zener diode is uses as a constant voltage source B. The SCR is a silicon rectifier with a gate electrode to control when current flows from cathode to anode C. The gate electrode in the FET corresponds to the collector in a bipolar transistor D. None of the above

149

28. Which of the following represents the equivalent circuit of a crystal for crystal oscillator?

A. Figure A B. Figure B C. Figure C D. None of the above

29. In high frequency region, an amplifier behaves like a

A. band pass filter B. low pass filter C. high pass filter D. any of the above

30. In a CE amplifier circuit the load resistance is open circuited. The output voltage will

A. increase B. decrease C. become zero D. increase or decrease

31. The configuration of figure is a

A. Hartley oscillator B. Precision Integrator C. Wienbridge oscillator D. Butterworth high pass filter

150

32. Which of the following combinations has no phase inversion of the signal?

A. Two CE stages B. CE and CC stages C. Three CE stages D. CE stages and emitter follower

33. IF amplifiers for radio receivers are often tuned to

A. 456 Hz B. 456 kHz C. 3456 MHz D. 456 GHz

34. The ripple factor of a full wave rectifier is about 0.5 A. True B. False

35. In a good voltage amplifier, its input impedance

A. must be high compared to the resistance of the source B. must be low compared to the resistance of the source C. must be equal to the resistance of the source D. must be half the resistance of the source

36. A Colpitt's oscillator uses

A. a tapped inductor B. an inductor and two capacitors C. both (a) and (b) D. either (a) or (b)

37. Assertion (A): Direct coupled amplifiers are rarely used

Reason (R): Direct coupled amplifiers suffer from the disadvantage of drift


151

38. In figure VCEQ for each transistor is

A. VCC B. 0.5 VCC C. 0.75 VCC D. 0.25 VCC

39. Class C operation finds application in

A. RF power amplifiers B. frequency multipliers C. both (a) and (b) D. neither (a) nor (b)

40. In which amplifier circuit is gate conductance negligible?

A. JFET amplifier B. MOSFET amplifier C. Both JFET and MOSFET amplifier D. None of the above

41. Which of the following is not necessarily the advantages of a push pull amplifier?

A. It gives more output B. It removes odd a well as even harmonics C. There is no effect of ripple of the power supply D. It consumes least power

42. In a feedback series regular circuit, the output voltage is regulated by controlling the

A. magnitude of the I/P voltage B. gain of the feed back BJT C. reference Voltage D. voltage drop across the series pass transistor

152

43. For operation of enhancement only N-channel MOSFET, value of gate voltage has to be

A. zero B. low positive C. high negative D. high positive

44. In a practical oscillator, the magnitude of loop gain Aβ is kept slightly larger than unity and the amplitude of oscillations is limited by

A. the ratio of A to β B. the on set of non-linearity of amplifying device C. the linearity of amplifying device D. all of the above

45. In figure output impedance of amplifier is

A. RE

B.

C.

D. re + RE

46. A non-inverting voltage feedback amplifier is a

A. voltage amplifier B. current amplifier C. current to voltage converter D. voltage to current converter

47. The upper end of the d.c. load line is called the __________ point and the lower end is the __________ point.

A. cut off, saturation B. saturation, active C. saturation, cut off D. active saturation

153

48. The transistor specification number 2N refers to

A. triac B. diac C. junction transistor D. FET with one gate

49. Which of the following components is essential for a voltage multiplier circuit?

A. Resistor B. Inductor C. Capacitor D. Both (a) and (c)

50. An ideal op-amp has

A. infinite input and output resistance B. low input and output resistance C. low input and high output resistance D. infinite input resistance and zero output resistance

Answer of Analog digital : CMOS, Darlington Pair

1‐>2 , 2‐>2 , 3‐>2 , 4‐>3 , 5‐>3 , 6‐>1 , 7‐>4 , 8‐>4 , 9‐>4 , 10‐>2 , 11‐>2 , 12‐>3 , 13‐>4 ,

14‐>2 , 15‐>3 , 16‐>3 , 17‐>3 , 18‐>2 , 19‐>1 , 20‐>3 , 21‐>1 , 22‐>2 , 23‐>3 , 24‐>4 , 25‐>3

, 26‐>4 , 27‐>4 , 28‐>3 , 29‐>2 , 30‐>1 , 31‐>3 , 32‐>1 , 33‐>2 , 34‐>1 , 35‐>1 , 36‐>3 , 37‐

>1 , 38‐>2 , 39‐>3 , 40‐>2 , 41‐>2 , 42‐>4 , 43‐>4 , 44‐>2 , 45‐>3 , 46‐>1 , 47‐>3 , 48‐>3 ,

49‐>3 , 50‐>4

154

Analog Electronics

Section16:CouplingCapacitor1. A multivibrator can be used as a A. cavity resonator B. harmonic generator C. wave form modifier D. any of the above 2. Which of the following circuit can operate class AB for audio power output? A. Push pull B. Cascade C. Pull down D. Darlington pair

3. Oscillation frequency in colpitt's oscillator is

A.

B.

C.

D. none of these 4. Which of the following circuit would be preferred for a 355 KHz IF amplifier? A. Resistance loaded B. Double tuned transformer C. Video amplifier D. Class C 5. Which of the following is not valid in case of bipolars? A. It has a low input impedance B. It has high voltage gain C. It is a current controlled device D. It is difficult to bias 6. For oscillations to starts, the loop gain A β of the oscillator must be initially A. less than unity B. 0.5 C. 1.0 D. more than unity

155

7. Ebers Moll model is applicable to A. bipolar Junction transistor B. N MOS transistor C. unipolar junction transistor D. field effect transistor 8. A transistor amplifier with 85% efficiency is expected to be A. class A B. class B C. class C D. class AB 9. Common emitter transistor has A. high current and high voltage gain B. low current gain and low voltage gain C. high current gain and low voltage gain D. low current and voltage gain 10. Which of the following is not the main characteristic of a FET? A. Drain resistance B. Forward transconductance C. Temperature stability D. Amplification factor 11. In figure the source resistance of current source IEE is infinite, then common mode gain is

A. infinite B. zero C. indeterminate

12. Generally op amp is used in A. open loop B. closed loop C. cascaded loop D. either (a) or (c)

156

13. To obtain very high I/P and O/P impedances in a feedback amplifier, the topology used is A. voltage series B. current series C. voltage shunt D. current shunt 14. A FET A. has two P-N junctions B. has three P-N junctions C. depends on the variation of the depletion layer width with reverse voltage, for its operation D. depends on the variation of a magnetic field for its operation 15. Pick the Odd one out A. MOSFET B. FET C. Planer transistor D. Unijunction transistor 16. The gate-source voltage that reduces the drain current to approximately zero is called A. gate-source on voltage B. gate-source voltage C. pinch-off voltage D. gate-source cut-off voltage 17. The basic amplifier in Weinbridge oscillator consists of A. CE stage followed by CE B. CE stage followed by CB C. CB stage followed by CE D. CC stage followed by CE 18. The advantage of transistor over vacuum tube is A. no heat is required B. small size and light in weight C. very low power consumption D. all of the above 19. Which of the following is necessary transistor action? A. The base region must be very wide B. The base region must be very narrow C. The base region must be made of some insulating material D. The collector region must be heavily doped 20 Which of the following is the point of reference JFET? A. Drain B. Gate C. Source D. None of the above

157

21. The equivalent circuit of an op-amp has A. a virtual ground at input B. a virtual ground at output C. virtual ground at input as well as at output D. none of the above

22. A distorted sinusoidal has the amplitudes A1, A2, A3 ... of the fundamental, second, harmonic third harmonic, ... respectively. The total harmonic distortion is

A.

B.

C.

D.

23. Class A amplifiers are preferred when A. minimum distortion is required B. maximum voltage gain is required C. output signal is desired in phase with input signal D. signal having A.C. superimposed on D.C. are to be amplified 24. In a half wave voltage doubler circuit the input frequency is 50 Hz. The ripple frequency is A. 25 Hz B. 50 Hz C. 100 Hz D. 150 Hz 25. Negative feedback in amplifier A. reduces gain B. increases frequency and phase distortion C. reduces bandwidth D. increases noise 26. If the changes in zener current in a voltage regulator circuit are too large, it can be corrected by using a A. emitter follower B. CE amplifier C. capacitor D. either (a) or (b)

158

27. A transistor has collector emitter base In a N-P-N transistor the electron flow into the transistor at A. I only B. II only C. II and III only D. I and II only 28. Assertion (A): In CC amplifier the collector is at ac ground Reason (R): CC amplifier is also called emitter follower A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 29. In figure the potential of gate terminal is

A. 4 V B. -4 V C. 0 D. 20 V

30. The derating factor, for ambient temperature higher than specified, for a transistor is about A. 2.5 mW/°C B. 0.5 mW/°C C. 10 mW/°C D. 20 mW/°C 31. The purpose of using negative feedback in a op-amps is to A. stabilize overall gain B. increase output C. stabilize overall gain and increase output D. increase output and decrease input

159

32. MOS circuits as compared to bipolar circuits take A. more chip area B. less chip area C. same chip area D. none of these 33. In a transistor with normal bias A. the emitter junction has a low resistance B. the emitter junction has a very high resistance C. the emitter junction supplies majority carries into the base region D. none of the above 34. The input resistance of JFET ideally approaches A. zero B. 1 ohm C. 100 ohm D. infinity 35. Typical values of voltage gain for CE, CB and CC amplifiers are A. 100, 100 and 1 respectively B. 100, 1 and 100 respectively C. 100, 1 and 1 respectively D. 1, 100 and 100 respectively 36. The circuit of figure is called

A. diode bias B. current mirror C. complementary mirror D. none of the above

37. CMOS is widely used in A. digital wrist watches B. analog circuits C. high power circuits D. all of the above

160

38. For a sinusoidal input, the circuit shown in the figure will act as a

A. Pulse generator B. Full wave rectifier C. Ramp generator D. Voltage Doubler

39. In the case of the circuit shown in the figure Vio = 10 mV dc maximum, the maximum possible output offset voltage Voo caused by the input offset voltage Vio with respect to ground is

A. 60 mV dc B. 110 mV dc C. 130 mV dc D. 150 mV dc

40. An op-amp is fed from a signal source through resistance R1. If it is to work as sign changer, the feedback resistance Rf should be A. equal to R1 B. twice R1 C. half R1 D. either (b) or (c)

161

41. In a series regulated power supply circuit, the voltage gain Av, of the 'pass' transistor satisfies the condition A. Av → ∞ B. 1 << Av < ∞ C. Av ≈ 1 D. Av << 1 42. A JFET can operate on A. enhancement mode only B. depletion mode only C. both depletion as well as enhancement modes D. neither depletion nor enhancement mode 43. A three terminal monolithic IC regulator can be used as A. an a adjustable output voltage regulator alone B. an adjustable output voltage regulator & a current regulator C. a current regulator & a power switch D. a current regulator alone 44. A Darlington pair consist of A. two CB amplifiers B. two CC amplifiers C. two cascaded CC amplifiers D. two cascaded CE amplifiers 45. Efficiency of a half wave diode rectifier is less than 40%. A. True B. False 46. A multivibrator generates A. sinusoidal waveforms B. non-sinusoidal waveforms C. both (a) and (b) D. none of the above 47. For a transistor if adc = 0.98 and emitter current IE is 2 mA, then collector current will be A. 0.44 mA B. 0.88 mA C. 1.96 mA D. 3.32 mA 48. The circuit consisting of two transistor connected in series with the d.c. supply voltage is called A. push pull B. differential pair C. stacked V+ D. complementary symmetry 49. Which of the following is the fastest switching device? A. JFET B. BJT C. MOSFET D. Triode

162

50. In a CE amplifier circuit, the output voltage A. is very small B. is always constant C. depends on β D. none of the above

Answer of Analog digital : Coupling Capacitor

1‐>3 , 2‐>1 , 3‐>1 , 4‐>2 , 5‐>4 , 6‐>4 , 7‐>1 , 8‐>3 , 9‐>1 , 10‐>3 , 11‐>1 , 12‐>2 , 13‐>3 ,

14‐>2 , 15‐>4 , 16‐>3 , 17‐>1 , 18‐>4 , 19‐>2 , 20‐>3 , 21‐>1 , 22‐>2 , 23‐>1 , 24‐>2 , 25‐>1

, 26‐>1 , 27‐>4 , 28‐>1 , 29‐>3 , 30‐>1 , 31‐>1 , 32‐>2 , 33‐>1 , 34‐>4 , 35‐>1 , 36‐>3 , 37‐

>1 , 38‐>2 , 39‐>3 , 40‐>1 , 41‐>3 , 42‐>2 , 43‐>4 , 44‐>3 , 45‐>1 , 46‐>1 , 47‐>2 , 48‐>3 ,

49‐>3 , 50‐>3

163

Analog Electronics

Section17:RectifierCircuits,Impedance1. In a voltage regulator circuit using zener diode the load voltage is nearly constant only if A. zener current is very small B. zener current is very large C. zener current is neither small nor large D. None of the above

2. The emitter resistor RE in the emitter of CE amplifier stabilizes the dc operating point against variation in A. temperature only B. β of transistor C. both temperature and β D. none of the above

3. In figure VCE (sat) = 0.1 V. Then IC (sat) =

A. 10 mA B. 20 mA C. 30 mA D. 40 mA

4. In case of a transistor amplifier the emitter resistance Re is removed A. the gain of the amplifier will reduce B. heat sink will not be required C. Q-point will become unstable D. base to emitter function will be less forward biased 5. Assertion (A): In monolithic IC the components are part of one chip Reason (R): An op-amp is a high gain dc amplifier A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 6. The absolute values of pinch-off voltage and gate-source cut-off voltage are A. nearly zero B. complementary to each other C. never equal D. equal

164

7. The common-drain amplifier, better known as the source follower, has a voltage gain __________ and the output signal is __________ with the input signal. A. approaching unity, in phase B. approaching unity, out of phase C. is very high, in phase D. is very high, in reverse phase 8. A ripple in collector supply voltage of the output stage of amplifier causes noise. A. True B. False 9. In CB amplifier the distortion of the input voltage waveform may occur due to A. very low input resistance of an amplifier B. very high input resistance of the amplifier C. improper biasing D. ripples in power supply 10. In a transistor IE = 10 mA, ICO = 0.5 μA and a = 0.995. Then ICEO = A. 100 μA B. 25 μA C. 10.1 mA D. 10.5 mA 11. The circuit of figure is

A. positive clipper B. negative clipper C. combination clipper D. either (a) or (b)

12. The ac input voltage of an amplifier A. is always equal to ac signal voltage B. may be equal to or more than ac signal voltage C. is always less than ac signal voltage D. may be equal or more or less than ac signal voltage

165

13. Symbol shown in figure represents a

14. In oscillators class C operation is preferred because A. is most efficient B. has frequency stability C. gives larger output D. it produces nearly square waves 15. If the Q of a single-stage single-tuned amplifier is doubled, then its bandwidth will A. remain same B. become half C. become doubled D. become four times 16. A boot strap generally incorporates A. CB configuration B. CE configuration C. emitter follower D. none of the above 17. If a common emitter amplifier with an emitter resistance RC has an overall transconductance gain of 1 m A/V, a voltage gain of - 4 and desensitivity of 50, then the value of the emitter resistance R would be A. 50 kω B. 0.98 kω C. 50 ω D. 0.98 ω 18. In an amplifier if conductor during the cycle is from 0 to 90° and again from 180° to 270°, the amplifier will be termed as A. class A B. class B C. class C D. class AB

166

19. Figure shows basic Hartley oscillator configuration. Do you think the polarities marked for the split coiled are correct?

A. yes they are B. no they are not C. it really doesn't matter D. none of the above

20. Assertion (A): Electric coupling, magnetic coupling and ground loop can cause unwanted high frequency oscillations. Reason (R): Hartley oscillator uses a tapped inductor A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

21. A three-section RC phase shift oscillator has R = 10K ohms and C = 0.001 μF. The frequency of oscillations is A. 1.1 kHz B. 2.5 kHz C. 3.3 kHz D. 6.5 kHz 22. Assertion (A): The ac load line is different from dc load line Reason (R): The ac load resistance seen by collector and emitter is different from dc load resistance A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 23. Assertion (A): A self bias circuit is the most commonly used bias circuit for bipolar junction transistors Reason (R): A self bias circuit limits the increase in collector or emitter current due to change in junction temperature. A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

167

24. As compared to full wave rectifier, a half wave rectifier A. has higher ripple factor B. has lower ripple factor C. may have higher or lower ripple factor D. has same ripple factor 25. When a transistor is to be at a temperature above 25°C A. smaller heat sink be provided B. maximum power rating be derated C. biasing circuit must be strengthened D. earth connections must be connected through a resistor 26. Harmonic distortion in CB amplifier may be least when the load resistance is A. negligible B. very low C. very high D. infinite 27. In a class C operation VCC = 40 V and VCE(sat) = 0.4 V. The efficiency is A. 90% B. 49.5% C. 1% D. 0.5% 28. In the case of the circuit shown in the figure, the collector current IC will be, if β = 100, VBE = 0.7 V, ICO = 0.1 βA at 20°C

A. 2.26 mA B. 1.85 mA C. 0.357 mA D. 0.185 mA

29. Which of the following statement is wrong? A. A depletion type N-channel MOSFET conducts even when VGS = 0 B. A BJT is very sensitive to radiation whereas FET is relatively immune C. Bipolars need higher supply voltage than FETs D. Both N-channel as well as p-channel JFETs work in the depletion mode

168

30. A sine wave with slew rate distortion looks like A. step wave B. square wave C. triangular wave D. cosine wave

31. Which of the following circuit does not need a coupling capacitor? A. Resistance loaded B. Transformer coupled C. Impedance coupled D. Single tuned

32. Turn on time of a transistor switch is equal to sum of (where tr is rise time, td is delay time) A. ts - tr B. ts - tf C. td + tr D. 2tr

33. In the re model of a BJT amplifier, the ac resistance of diode at room temperature is about (IE is quiescent emitter current)

A.

B.

C.

D.

34. Power transistors are invariably provided with A. soldered connections B. heat sink C. metallic casing D. none of the above 35. The most widely used LC oscillator is A. Hartley oscillator B. Crystal oscillator C. Colpitt's oscillator D. Clapp's oscillator 36. A transistor with a = 0.98 then β will be A. 49 B. 50 C. 47 D. 48

169

37. In amplifiers, the parasitic oscillation result due to A. transistor inter junction capacitance B. push pull operator C. negative feedback D. poor inter-stage coupling 38. Assertion (A): Negative feedback reduces the gain of an amplifier Reason (R): Negative feedback is very commonly used in amplifier circuits A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 39. The stray capacitance between the last stage and the first stage of an oscillator may cause A. unwanted low frequency oscillations B. unwanted high frequency oscillations C. unwanted oscillations at low and high frequencies D. large feedback 40. Assertion (A): A large negative feedback is deliberately introduced in an amplifier to make its gain independent of variation is in parameters of active device and other components. Reason (R): A large negative feedback results in a high value of return difference compared to unity which makes the feedback gain inversely proportional to feedback factor. A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 41. In figure the coordinates of Q point on the load line are (Neglect VBE)

A. IC = 10 mA, VCE = 15 V B. IC = 5 mA, VCE = 22.5 V C. IC = 5 mA, VCE = 15 V D. IC = 10 mA, VCE = 22.5 V

170

42. Lower chip area requirements of MOS is advantage in A. low power circuits B. high power circuits C. repetitive operation circuits D. large scale integration 43. For the circuit shown in the figure, the capacitor C is initially uncharged. At t = 0, the switch S is closed. The voltage Vc across the capacitor at t = 1 millisecond is (In the figure shown above, the op-amp is supplied with ± 15 V and the ground has been shown by the symbol)

A. 0 V B. 6.3 V C. 9.45 volts D. 10 volts

44. The circuit shown in figure will

A. oscillate at 456 kHz B. oscillate at 228 kHz C. oscillate at microwave frequency D. not oscillate

45. Assertion (A): In an op-amp the gain bandwidth product equals ffinity Reason (R): The change in open loop gain of an amplifier has almost no effect on closed loop gain A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

171

46. A radio frequency choke permits an easy flow of __________ current and at the same time it offers a very impedance to __________ currents. A. A.C., low frequency B. A.C., high frequency C. D.C., low frequency D. D.C. high frequency 47. In a common emitter circuit all voltages are measured with respect to A. base B. emitter C. collector D. base or collector 48. As a compared to a CB amplifier, a CE amplifier has A. lower current amplification B. higher current amplification C. lower input resistance D. higher input resistance 49. For high frequency response of a transistor amplifier, suitable model to use is A. Kelvin network B. Lattice network C. Hybrid p D. T-network 50. n the analysis of common emitter amplifier we may neglect A. hre B. hoe C. hfe D. hie

Answer of Analog digital : Rectifier Circuits, Impedance

1‐>1 , 2‐>3 , 3‐>2 , 4‐>3 , 5‐>2 , 6‐>4 , 7‐>1 , 8‐>1 , 9‐>1 , 10‐>1 , 11‐>3 , 12‐>4 , 13‐>1 ,

14‐>4 , 15‐>2 , 16‐>1 , 17‐>2 , 18‐>2 , 19‐>2 , 20‐>2 , 21‐>4 , 22‐>1 , 23‐>1 , 24‐>1 , 25‐>2

, 26‐>3 , 27‐>1 , 28‐>1 , 29‐>3 , 30‐>3 , 31‐>2 , 32‐>3 , 33‐>1 , 34‐>2 , 35‐>1 , 36‐>1 , 37‐

>1 , 38‐>2 , 39‐>2 , 40‐>1 , 41‐>1 , 42‐>4 , 43‐>4 , 44‐>4 , 45‐>2 , 46‐>4 , 47‐>2 , 48‐>2 ,

49‐>3 , 50‐>1

172

Analog Electronics

Section18:DEMOSFET,SwampedAmplifier1. To draw dc equivalent circuit for a CE amplifier circuit we should A. Reduce all ac sources to zero B. Open all capacitors C. Reduce all ac sources to zero and open all capacitors D. Reduce all ac sources to zero and short all capacitors 2. Which amplifier has the higher power gain? A. Common emitter B. Common collector C. Common base D. Both CC and CE 3. A low noise device is most important A. at front end of equipment B. in the last stage of equipment C. in the middle stages of equipment D. both (b) and (c) 4. The circuit shown I/P in the figure represents

A. Low pass filter B. High pass filter C. Band Pass filter D. Band stop filter

5. The D.C. alpha(a) of a transistor is approximately A. unity B. 10 to 50 C. 100 to 500 D. 1000 to 5000 6. Which of the following statement about JFET is true? A. In a JFET, gate and source have opposite polarity with respect to drain irrespective of the type of FET B. In its schematic symbol for JFET, the arrow always points to p-type material C. In an n-channel JFET, the channel is the narrowest under zero gate bias condition D. In JFET, gate source cut off voltage is numerically equal to the pinch off voltage

173

7. When a CE transistor is cut off A. voltage across collector reduces to zero B. voltage across collector is maximum C. maximum collector current flows D. maximum voltage appears across the load resistance 8. Which of the following are linear ICs? A. RF and IF amplifiers B. Wide band amplifier C. Audio amplifiers D. All of the above 9. In a transistor, current ICBO flow when A. some D.C. voltage is applied in the reverse direction to the emitter junction with the collector open circuit B. some D.C. voltage is applied in the forward direction to the collector junction with the emitter open circuit C. some D.C. voltage is applied in the reverse direction to the collector junction with the emitter open circuited D. some D.C. voltage is applied in the forward direction to the emitter junction with the collector open circuited 10. The theoretical maximum efficiency of a half wave diode rectifier is A. 40.6% B. 50% C. 81.2% D. slightly less than 100% 11. In a class C power amplifier A. resonant frequency of tuned circuit is equal to fundamental frequency of pulsed waveform B. resonant frequency of tuned circuit is half the fundamental frequency of pulsed waveform C. resonant frequency of tuned circuit has no relation to the fundamental frequency of pulsed waveform D. either (b) or (c) 12. An engineer designs an amplifier to have a voltage gain of 60, but when constructed it only had a gain of 50. How much feedback should be used to provide the desired level? A. +0.03% B. +0.33% C. +1.30% D. +3.3% 13. Consider the following rectifier circuits : half-wave rectifier without filter full-wave rectifier without filter full-wave rectifier with series inductance filter full-wave rectifier with capacitance filter. The sequence of these rectifier circuits in decreasing order of their ripple factor is A. 1, 2, 3, 4 B. 3, 4, 1, 2 C. 1, 4, 3, 2 D. 3, 2, 1, 4

174

14. The disadvantage of FET over BJT is A. poor high frequency performance B. low power-handling ability C. low values of voltage gain D. all of the above 15. In a cascade amplifier, the intermediate stages are always in A. CC configuration B. CB configuration C. CE configuration D. any of the above 16. The gain of a source follower is unity. A. True B. False 17. V MOS have the advantage of A. faster switching B. no thermal run away C. both (a) and (b) D. none of the above 18. For the high-pass circuit to act as a differentiator, the time constant must be A. small B. very small in comparison to the time period of the input signal C. very high in comparison to the time period of the input signal (that is low pass circuit) D. moderate value 19. The bandwidth of an amplifier can be reduced by A. miller effect compensation B. pole zero compensation C. dominant pole compensation D. lead compensation 20. The depletion type MOSFET can operate in A. depletion mode only B. enhancement mode only C. depletion or enhancement mode D. neither depletion nor enhancement mode

175

21. The circuit shown in the figure is that of

A. non-inverting amplifier B. Inverting amplifier C. an oscillator D. Schmitt trigger

22. Which of the following oscillator circuits uses three capacitors in the phase shifting network? A. Hartley B. Clapp C. Colpitt's D. Both (b) and (c) 23. In figure, D2 turns on when

A. vi is more positive than V1 B. vi is less positive than V1 C. vi is more negative than V2 D. vi is less negative than V2

24. 2N 2430 could be a A. semi-conductor diode B. dual gate MOSFET C. BJT D. UJT

176

25. The current through common emitter resistor of a differential amplifier is called A. differential current B. emitter current C. ground current D. tail current 26. Figure shows the feedback network of one of the very popular types of sinusoidal oscillators. Which one is that?

A. Weinbridge oscillator B. Hartley oscillator C. Colpitt's oscillator D. R-C phase shift oscillator

27. If re is ac resistance of diode, the Thevenin input impedance of a differential amplifier is A. re B. bre C. 2 bre D. 0.5 bre 28. One of the following can be used to generate a pulse whenever triggered A. flip-flop B. monostable multivibrator C. stable multivibrator D. Schmitt trigger 29. With JFETs cascade means A. a common source driving a common gate connection B. a common gate driving a common source connection C. two FETs connected in parallel D. none of the above 30. In figure the trace on the CRO will be

A. half rectifier wave B. clamped wave C. no trace at all D. either (a) or (b)

177

31. In a differential amplifier, CMRR can be improved by using an increased A. emitter resistance B. collector resistance C. power supply voltages D. source resistance 32. A push pull amplifier is a A. power amplifier B. voltage amplifier C. current amplifier D. both power and current amplifier 33. How many cascaded stage of CE amplifiers will result in polarity inversion of the input signal? A. Two B. Three C. Four D. None 34. The more negative gate voltage, the conductive channel becomes A. narrower B. wider C. thicker D. linear 35. A JFET is a A. unipolar device B. bipolar device C. tripolar device D. none of the above 36. When negative feedback is used the fractional changes in closed loop gain are desensitized by the factor (1 + Avβ) A. True B. False 37. Circuit shown in the figure is

A. astable multivibrator B. monostable multivibrator C. VCO D. ramp Generator

178

38. The h parameter equivalent to ac resistance re is A. hib B. hfe C. hob D. hrb

39. To have a centred Q point in CE amplifier

A. ac resistance of collector circuit

B. ac resistance of emitter circuit

C. ac resistance of collector and emitter circuit

D. ac resistance of collector and emitter circuit

40. The maximum efficiency of class A amplifier is A. 100% B. 81.8% C. 50% D. 40% 41. Symbol shown in figure represents a

A. P-channel DEMOSFET B. N-channel DEMOSFET C. UJT with N-type base D. UJT with P-type base

42 In a transistor push pull amplifier A. there is no dc present in the output B. there are no even harmonics in the output C. both (a) and (b) D. neither (a) nor (b) 43. Which circuit has its output signal from, the emitter? A. Common base B. Common emitter C. Emitter follower D. None of the above

179

44. In a self bias circuit for CE amplifier, the base voltage is A. equal to supply voltage B. more than supply voltage C. equal to or more than supply voltage D. less than supply voltage 45. In figure the diode is ideal (zero cut in voltage zero forward resistance). Then the current through diode is

A. 0 B. 4 A C. 1 A D. none of the above

46. In CE approximation, the upper end of d.c. load line is called the __________ point and the lower end is the __________ point. A. Q, base B. base, Q C. saturation, cut off D. cut off, saturation 47. Which of the following is the common feature between FETs and bipolars? A. Have low input impedance B. Have low voltage gain C. Are difficult to bias D. None of them 48. Which of the following statement is correct? A. The input impedance of CE amplifier is usually around 10 ω B. The voltage gain of a transistor amplifier in CE mode is always less than unity C. The output impedance of a transistor amplifier is independent of the transistor configuration D. The voltage gain of a transistor amplifier is independent of the load resistance 49. For an amplifier the power gain in decibels will be equal to voltage gain in decibels only when A. R0 = 0 B. R0 = Ri = 90 C. R0 = Ri D. Ri = 0 50. For an op-amp source follower circuit A. input and output voltages have same magnitude B. output and input voltages are in phase C. output and input voltages are in phase but have different magnitudes D. output and input voltages have same magnitude and are in phase

180

Answer of Analog digital : DEMOSFET, Swamped Amplifier

1‐>3 , 2‐>1 , 3‐>1 , 4‐>3 , 5‐>1 , 6‐>4 , 7‐>2 , 8‐>4 , 9‐>3 , 10‐>1 , 11‐>1 , 12‐>2 , 13‐>1 ,

14‐>4 , 15‐>3 , 16‐>1 , 17‐>3 , 18‐>2 , 19‐>3 , 20‐>3 , 21‐>4 , 22‐>2 , 23‐>3 , 24‐>3 , 25‐>4

, 26‐>1 , 27‐>3 , 28‐>2 , 29‐>1 , 30‐>3 , 31‐>1 , 32‐>1 , 33‐>2 , 34‐>1 , 35‐>1 , 36‐>1 , 37‐

>1 , 38‐>1 , 39‐>3 , 40‐>3 , 41‐>3 , 42‐>3 , 43‐>3 , 44‐>4 , 45‐>3 , 46‐>3 , 47‐>4 , 48‐>1 ,

49‐>3 , 50‐>3

181

Analog Electronics

Section19:OpenLoopConfiguration1. Which circuit is called swamped amplifier? A. CC B. CE C. CB D. Both (a) and (b) 2. Whenever a JFET operates above pinch-off voltage A. depletion regions become smaller B. drain current increase steeply C. drain current starts decreasing D. drain current remains nearly constant 3. Assertion (A): The horizontal intercept of dc load line is the same as ideal cut off point Reason (R): When a transistor is in cut off region, collector current is zero A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 4. In an oscillator the total phase shift around the loop must be A. 180° B. 90° C. 270° D. 0° 5. Assertion (A): Linear ICs include audio amplifier, wideband amplifier, RF amplifier and IF amplifier Reason (R): The error voltage in a feedback circuit is very small A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong 6. Which op-amp circuit uses a resistance in series with input and capacitor in feedback path? A. Differentiating amplifier B. Integrating amplifier C. Logarithmic amplifier D. Exponential amplifier 7. If the plate supply voltage for a plate modulated class C amplifier is E volts, the maximum plate-cathode voltage could be almost as high as A. E B. E/2 C. 2E D. 4E 8. An engineer designs an amplifier to have a voltage gain of 60, but when constructed it only had a gain of 50. Which of the following will increases from this type of operation? A. Stability B. Bandwidth C. Distortion D. Input resistance

182

9. Low gain-bandwidth product of a JFET is due to A. reduced number of holes B. junction capacitive effects C. low degree of isolation between input and output D. all of the above 10. Common base configuration is little used because A. it has low input impedance B. it has high input impedance C. it does not heat up D. it has very high gain 11. Assertion (A): An ac amplifier uses coupling capacitors at input and output Reason (R): The capacitive reactance varies inversely with frequency. It is infinite for dc A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 12. The changes in ambient temperature affect the open loop gain of amplifier. A. True B. False 13. A semi-conductor device that behaves like two SCRs is A. UJT B. MOSFET C. JFET D. TRIAC 14. A collector collects A. electrons from the base in case of N-P-N transistor B. electrons from the emitter in case P-N-P transistor C. holes from the base in case of N-P-N transistor D. holes from the base in case of P-N-P transistor 15. The input gate current of a FET is A. a few amperes B. a few milli amperes C. a few micro amperes D. negligible 16. When a JFET is cut off, it's like an __________ switch and when it is saturated, it's like a __________ switch. A. closed, open B. open, closed C. open, open D. closed, closed

183

17. Following figure is a signal conditioning Amplifier, changes gain depending upon the polarity of Vs. What will be circuit voltage gain for + Vs and for - Vs if D2 is ideal.

A. AV = -R3/R1 B. R3/R1 C. R1/R3 D. 1 + R3/R1

18. In a full wave diode rectifier circuit each diode carries current for A. 90° in each cycle B. 180° in each cycle C. 270° in each cycle D. 360° in each cycle 19. In a JFET, the lower end is called the __________ and the upper end is called the __________ . A. source, channel B. channel, drain C. source, drain D. drain source 20. RC network shown in the given figure can provide a maximum theoretical phase shift of

A. 90° B. 180° C. 270° D. 360°

21. If a capacitor C is charged by a constant current I, then the rate of change of voltage with time given by sweep speed equal to A. C/I B. IC C. I/C

184

22. In operational Amplifier, Common mode voltage gain should be A. 0 B. ∞ C. 1 D. 0.5 23. Which of the following is non-sinusoidal oscillator? A. Multivibrator B. Relaxation oscillator using UJT C. Relaxation oscillator using tunnel diode D. Any of the above 24. The circuit of the figure is an example of feedback of the following type

A. current series B. current shunt C. voltage series D. voltage shunt

25. Which class of amplifiers operates with least distortion? A. Class A B. Class B C. Class C D. Class AB 26. The enhancement type MOSFET is called a A. normally on MOSFET B. normally off MOSFET C. P-type MOSFET D. N-type MOSFET 27. Saturation of iron core causes distortion. A. True B. False 28. The mobility of e- for Ge and Si respectively is A. 1.66, 2.5 B. 2.5, 1.66 C. 2.7, 2.33 D. 2.33, 2.7

185

29. If three cascaded stages of amplifier have gains 10, 20 and 30 the overall voltage will be A. 30 B. 60 C. 600 D. 6000 30. Which of the following statement is incorrect? A. UJT is a 3-terminal diode having two unequally doped regions B. A UJT can be triggered by any one of its three terminals C. The bi-directional switching characteristics of a diac are symmetrical D. As compared to JFETs, MOSFETs generate less noise in high gain amplifiers 31. The circuit shown in figure will act as

A. differentiator B. adder C. clipper D. clamper

32. Which of the following best represents the input impedance of an actual op-amp? A. 10 ohm B. 1 k ohm C. 1 M ohm D. 100 M ohm 33. For a transistor if adc = 0.98 and emitter current IE is 2 mA, then base current will be A. 10 μA B. 40 μA C. 80 μA D. 200 μA 34. In a resistance loaded, RC coupled amplifier the d.c. component is blocked by A. Transistor B. CC C. RB D. RC

186

35. In figure it is desired that output wave is symmetrical. Then

A. both diodes should be similar and |V1| = |V2| B. both diodes should be similar C. |V1| = |V2| D. either (a) or (b)

36. For maximum unclipped output from a CE amplifier, the Q point should be A. at the centre of dc load line B. at the centre of ac load line C. at the centre of collector current D. none of the above 37. In the op-amp circuit shown in figure the current through load resistance RL is

A.

B.

C.

D.

38. In a normally biased N-P-N transistor the main current crossing the collector junction is A. a drift current B. a hole current C. a diffusion current D. same as the base current

187

39. Which of the following parameters of CE circuit has the unit of ohms? A. hie B. hre C. hfe D. hoe

40. The ripple factor of a power supply is given by A. Pdc/Pac

B.

C.

D.

41. Which configuration has high input impedance and low output impedance? A. CB B. CE C. CC D. CB and CE 42. The input resistance of FET in the low frequency small signal operation is A. infinitely high B. around 1 kω C. around 50 ω D. very small 43. A Weinbridge oscillator is a A. VHF oscillator B. RF oscillator C. microwave oscillator D. audio frequency oscillator 44. As compared to a BJT amplifier circuit, a JFET amplifier circuit A. has low input impedance B. has high input impedance C. has very low input impedance D. may have either low or high input impedance

188

45. Assertion (A): In the circuit shown figure the diode is used to protect the active devices. Transistor T goes into saturation when a positive pulse is applied at base and non conducting Reason (R): When the current in an inductor is suddenly stopped, a high voltage is induced across it.


46. A logarithmic amplifier has diode in the feedback path. A. True B. False 47. The given circuit has a feedback factor of

A.

B.

C.

D.

48. When the ac input signal is very large the instantaneous operating point CE amplifier moves all the way between A. ac saturation and ac cut off points B. ac operating and ac cut off points C. ac saturation and ac operating points D. none of the above

189

49. For full wave rectification four diode bridge rectifier is claimed to have following advantages: Less expensive transformer Small size transformer Suitable for higher voltage applications Which of these are correct? A. 1 and 2 only B. 1 and 3 only C. 2 and 2 only D. 1, 2, 3 50. In a linear op-amp circuit A. the product of gain and bandwidth is constant B. input can be dc only C. input can be ac only D. saturation may occur

Answer of Analog digital : Open Loop Configuration

1‐>1 , 2‐>4 , 3‐>1 , 4‐>4 , 5‐>2 , 6‐>2 , 7‐>4 , 8‐>3 , 9‐>2 , 10‐>1 , 11‐>1 , 12‐>1 , 13‐>4 ,

14‐>2 , 15‐>4 , 16‐>2 , 17‐>1 , 18‐>2 , 19‐>3 , 20‐>2 , 21‐>3 , 22‐>1 , 23‐>1 , 24‐>4 , 25‐>1

, 26‐>2 , 27‐>1 , 28‐>1 , 29‐>4 , 30‐>4 , 31‐>3 , 32‐>3 , 33‐>1 , 34‐>2 , 35‐>1 , 36‐>2 , 37‐

>1 , 38‐>1 , 39‐>1 , 40‐>2 , 41‐>3 , 42‐>1 , 43‐>4 , 44‐>2 , 45‐>1 , 46‐>1 , 47‐>4 , 48‐>1 ,

49‐>4 , 50‐>1

190

Analog Electronics

Section20:Transistor1. In the equivalent circuit of figure voltage gain is

A.

B.

C.

2. In all base driver amplifiers A. ac collector voltage is 180° out of phase with ac base voltage B. ac emitter voltage is 180° out of phase with ac base voltage C. ac collector voltage is in phase with ac base voltage D. none of the above 3. For input and later stages, BI-FET op-amp use A. JFETs and MOSFETs respectively B. MOSFETs and JFETs respectively C. JFETs and BJTs respectively D. BJTs and JFETs respectively 4. The maximum theoretical efficiency for class A amplifier is A. 12.5% B. 25% C. 50% D. 75% 5. In the case of an amplifier, the normalised voltage gain is given by.

A. fP >> f0 B. fP = f0 C. fP << f0 D. f0 = 2 fP

191

6. The parameter β of a BJT change by 300%. If self bias is used in the amplifier using this BJT, the quiescent value of IC and VCE remain almost the same. A. True B. False

7. Oscillation frequency in Wein bridge oscillator is

A.

B.

C.

8. The horizontal intercept of dc load line is the same as ideal A. cut off point B. saturation point C. operating point D. quasi saturation point 9. In a diode rectifier with a capacitance input filter, a surge current is likely to flow when the circuit is switched on. The cause of this surge current is A. the non linear behaviour of diodes B. the capacitor acts as a short circuit at the instant of switching, C. the inductance of leads D. both (a) and (b) 10. In the op-amp circuit of figure, V0 =

A. 3 V1 - 4 V2 B. -3 V1 + 4 V2 C. 3(V1 - V2) D. -3(V1 - V2)

11. When a transistor is connected in common emitter mode, it with have A. negligible input resistance and high output resistance B. high input resistance and low output resistance C. medium input resistance and high output resistance D. low input resistance as well as output resistance

192

12. In which of the following circuits is op-amp used in open loop configuration? A. Comparator B. Summing amplifier C. Integrating amplifier D. Logarithmic amplifier 13. Assertion (A): A class C amplifier can also be used as frequency multiplier Reason (R): When narrow current pulses drive a resonant circuit the output can be a near perfect sine wave A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

14. In a CC circuit the current gain is

A.

B.

C.

15. In a CE amplifier the Q point is very close to saturation point on the dc load line. This results in A. positive clipping of collector current B. negative clipping of collector current C. both positive and negative clipping of collector current D. either positive or negative clipping of collector current 16. A transistor amplifier has poles at s1 = - 0.000245 x 109 rad/sec. s2 = - 0.0748 x 109 rad/sec. s3 = - 0.670 x 109 rad/sec. s4 = - 4.38 x 109 rad/sec. The upper 3 dB frequency of the amplifier will be A. s1 B. s1 + s2 + s3 + s4 C. s1 + s4 D. s4

193

17. The circuit of figure is called

A. current mirror B. voltage mirror C. impedance inversion D. phase splitting

18. A feedback network to be used with an amplifier to provide oscillation is tested and found to give an output of 0.124 V with a 0.5 V input. What must be the minimum gain of the oscillator to provide oscillations? A. 40 B. 60 C. 100 D. 130

19 In a closed loop non-inverting amplifier, constructed using single break-frequency op-amp, bandwidth with feedback can be written as. (f0 - break frequency, β - gain of the feedback circuit, A - open loop voltage gain, Af - closed loop voltage gain)

A.

B.

C.

D.

20. The common gate amplifier has a characteristically __________ input resistance and a __________ output resistance. A. low, low B. high, high C. low, high D. high, low

194

21. For the circuit of figure the input and output Miller resistances are

A. 5 kω each B. 1 ohm and 5 kω respectively C. 5 kω and 1 ohm respectively D. 1 ohm each

22. Calculate the O/P voltage of a non-inverting constant gain multiplier with R1 = 100 kω, Rf= 600 kω, V1 = 2 volt, then O/P voltage Vo of non inverting op-amp is given by A. 16 V B. 14 V C. 20 V D. 15 V 23. Assertion (A): A class C amplifier is a timed amplifier which needs a tank circuit as the load in the collector circuit of the transistor for its proper operation Reason (R): In class C operation collector current flows for less than 180° of the ac cycle and thus flows in pulses A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 24. The V MOS can handle __________ currents than a conventional MOSFET. A. much lower B. almost same C. almost half D. much larger 25. In a CE amplifier it is desired that the signal should be able to swing equally in both directions. Then the Q point should be A. at the centre of ac load line B. at the centre of dc load line C. at the centre of collector voltage D. at the centre of collector current 26. The emitter coupled pair of BJT's gives a linear transfer relation between the differential output voltage and the differential input voltage Vid only when the magnitude of Vid is less a times the thermal voltage, where a is A. 4 B. 3 C. 2 D. 1

195

27. Symbol shown in figure represents a

A. Enhancement only N-channel MOSFET B. UJT with p-type base C. N-channel DMOSFET with internal protection D. Phototransistor

28. In figure VCC = + 30 V, IC corresponding to Q point is 1 mA. If RC = 5 kω and RE = 5 kω, VCE corresponding to Q point is

A. 30 V B. 20 V C. 25 V D. 5 V

29. An engineer designs an amplifier to have a voltage gain of 60, but when constructed it only had a gain of 50. What value of feedback will double the gain? A. +0.5% B. +0.66% C. +1% D. +3.3% 30. A bypass capacitor produces A. dc ground B. ac ground C. both dc and ac ground D. none of the above 31. In order to rectify sinusoidal signals of millivolt range (< 0.6 V) A. bridge rectifier using diodes can be employed B. full wave diode rectifier can be used C. a diode is to be inserted in the feedback loop of an op-amp D. a diode is to be inserted in the I/P of an op-amp

196

32. For the circuit shown in figure low cut-off frequency is

A. 1.59 Hz B. 159 Hz C. 1.59 kHz D. 1.59 MHz

33. In a BJT amplifier circuit the size of coupling capacitor depends on A. lowest frequency B. highest frequency C. average of lowest and highest frequencies D. none of the above 34. The slope of the transfer characteristics of an N-channel JFET is A. positive B. negative C. constantly varying D. zero 35. A FET is a __________ controlled device whereas a bipolar transistor is a __________ controlled device. A. gate, drain B. drain, gate C. current, voltage D. voltage, current 36. In an op-amp differentiator A. the amplitude of output is proportional to rate of change of input B. the amplitude of output is proportional to input C. output occurs when input is finite and constant D. polarity of input and output is the same 37. In CE approximately, the active region is where the collector curves are A. almost horizontal B. almost vertical C. inclined at 45° D. inclined at 60°

197

38. In the circuit of figure for sinusoidal input the waveform of the output will be as shown in

A. figure A B. figure B C. figure C D. figure D

39. Which of the following statements is false? A. Push pull signals are equal and opposite in phase B. Class AB operation cannot be used for a push pull audio power output phase C. A push pull output transformer has a centre-tapped primary D. All of the above 40. The purpose of impedance matching in an amplifier circuit is to achieve A. high efficiency B. reduce distortion C. maximum power transfer D. none of the above 41. In the amplifier circuit figure the quiescent point voltage and current are

A. 12 V, 5 mA B. 12 V, 2 mA C. 10 V, 2 mA D. 10 V, 5 mA

198


A. NPN transistor B. PNP transistor C. Zener diode D. Power diode

43. In a JFET, gates are always A. forward biased B. reverse biased C. either forward or reverse biased D. unbiased 44. Assertion (A): As per Miller theorem a capacitance C from input to output appears as a much larger capacitance across input terminals Reason (R): In a lag network the output voltage appears across capacitor A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 45. CMRR of an op-amp is about 0.1. A. True B. False 46. In a base driver amplifier the voltage gain is the ratio of A. ac collector voltage to ac base voltage B. ac emitter voltage to ac base voltage C. ac collector voltage to ac emitter voltage D. ac base voltage to ac emitter voltage 47. In switching devices, gold doping is used to A. improve bonding B. reduce storage time C. increase the mobility of the carrier D. protect the terminals against cooperation 48. In a current mirror A. the i - v curve of compensating diode is similar to collector curve of transistor B. the i - v curve of compensating diode is similar to transconductance curve of transistor C. either (a) or (b) D. neither (a) nor (b)

199

49. are related asFor a BJT, β and

A.

B.

C.

D.

50. By connecting external resistances to a differential amplifier we can adjust A. voltage gain B. bandwidth C. both voltage gain and bandwidth D. none of the above 51. Assertion (A): A good op-amp should have very large band width Reason (R): An ideal op-amp should have infinite input resistance and zero output resistance A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 52. Assertion (A): A resistor is a passive load and a transistor is an active load Reason (R): Op-amp is mostly used in feedback mode A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct 53. A silicon sample A is doped with 1018 Atoms/cm3 of Boron. Another sample B of identical dimensions is doped with 1018 atoms/cm3 of phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of the sample A to B is A. 3 B. 1/3 C. 2/3 D. 3/2 54 Assertion (A): If power gain doubles the power gain increases by 3 dB Reason (R): The bel power gain of cascaded stages is equal to sum of each bel power gain A. Both A and R are correct and R is correct explanation for A B. Both A and R are correct but R is not correct explanation for A C. A is correct R is wrong D. A is wrong R is correct

200

55. A junction Field Effect Transistor can operate in A. depletion mode only B. enhancement mode only C. depletion and enhancement modes D. neither depletion nor enhancement modes 56. In deriving ac equivalent circuit for an amplifier circuit we short circuit A. all resistors B. all transistors C. all inductors D. all capacitors 57 In a CB amplifier the maximum efficiency could be A. 99% B. 85% C. 50% D. 25% 58. The noise figure of FET circuit is A. independent of the quiescent point B. dependent on the quiescent point only C. dependent on the triggering mechanism D. independent of all above 59. CMRR is the ratio of differential voltage gain to common mode gain. A. True B. False 60. In most transistor the collector region is made physically larger than the emitter region A. for dissipating heat B. to distinguish it from other regions C. as it is sensitive to ultraviolet rays D. to reduce resistance in the path of flow of electrons 61. The leakage current in CB configuration may be around A. few micro amperes B. few hundred micro amperes C. few milliamperes D. few hundred milliamperes 62. Which of the following amplifier circuit using junction transistor has the best gain? A. Common base B. Common emitter C. Common collector D. All have the same gain

201

63. The re model equivalent circuit shown in figure is for

A. CE amplifier B. CC amplifier C. CB amplifier D. None of the above

64. Which mode is usually preferred for cascading? A. CE B. CB C. CC D. Any of the above 65. In a rectifier only a portion of input power is converted into DC power. The rest is AC power. A. True B. False 66. Class-B amplifier has less efficiency compared to A. class A B. class B C. class C D. class A, AB and C 67. Figure shows a

A. bipolar transistor B. JFET C. p-channel MOSFET D. n-channel enhancement MOSFET

68. A certain transistor has adc of 0.98 and a collectors leakage current of 5 μA. If IE = 1 mA, the base current will be A. 35 μA B. 25 μA C. 15 μA D. 5 μA

202

69. Which of the following circuit has the greatest bandwidth? A. fr = 455 MHz; Q = 10 B. fr = 455 MHz; Q = 100 C. fr = 1 MHz; Q = 100 D. fr = 1 MHz; Q = 10 70. The encapsulation of transistor is necessary for A. preventing radio interference B. preventing photo-emission effects C. avoiding loss of free electrons D. mechanical ruggedness 71. The circuit diagram shown in the figure consists of transistors in;

A. parallel connection B. cascade connection C. darlington connection D. series connection

72. The signal input to a given amplifier is made up of 100 mω signal power and 1 mω noise power. The amplifier contributes an additional 100 mω of noise and has a power gain of 20 dB. The input signal-to noise ratio is A. 2 B. 10 C. 20 D. 100 73. Rise time in a transistor is change from A. 10% of its final value to 90% of its final value B. 0% of its final value to 90% of its final value C. 10% of its final value to 100% of its final value D. 10% to its final value to 50% of its final value 74. In a transistor leakage current mainly depends on A. doping of base B. size of emitter C. rating of transistor D. temperature

203

Answer of Analog digital : Transistor

1‐>2 , 2‐>1 , 3‐>3 , 4‐>2 , 5‐>1 , 6‐>1 , 7‐>1 , 8‐>1 , 9‐>2 , 10‐>2 , 11‐>3 , 12‐>1 , 13‐>2 ,

14‐>1 , 15‐>1 , 16‐>1 , 17‐>1 , 18‐>1 , 19‐>1 , 20‐>3 , 21‐>2 , 22‐>2 , 23‐>1 , 24‐>4 , 25‐>1

, 26‐>4 , 27‐>3 , 28‐>2 , 29‐>3 , 30‐>2 , 31‐>3 , 32‐>1 , 33‐>1 , 34‐>2 , 35‐>4 , 36‐>1 , 37‐

>1 , 38‐>4 , 39‐>2 , 40‐>3 , 41‐>3 , 42‐>1 , 43‐>2 , 44‐>2 , 45‐>2 , 46‐>1 , 47‐>2 , 48‐>2 ,

49‐>4 , 50‐>3 , 51‐>1 , 52‐>2 , 53‐>2 , 54‐>1 , 55‐>1 , 56‐>4 , 57‐>4 , 58‐>1 , 59‐>1 , 60‐>1

, 61‐>1 , 62‐>2 , 63‐>3 , 64‐>1 , 65‐>1 , 66‐>1 , 67‐>4 , 68‐>3 , 69‐>4 , 70‐>4 , 71‐>1 , 72‐

>4 , 73‐>1 , 74‐>3

204

electronics & communication engineering part ii · 2018. 6. 1. · analog electronics section 1...

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