iium electronics ece 1312/ece 1231 final exam sem 1 (2012- 2013)

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INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

END OF SEMESTER EXAMINATION

SEMESTER 1, 2012/2013 SESSION

KULLIYYAH OF ENGINEERING Programme : ENGINEERING Level of Study : UG 1

Time : 9:00 am- 12:00 pm Date : 06/01/13

Duration : 3 Hours

Course Code : ECE 1312/ECE 1231 Section(s) : 1 - 11

Course Title : Electronics

This Question Paper Consists of Eight (8) Printed Pages (Including Cover Page) With

Six (6) Questions.

INSTRUCTION(S) TO CANDIDATES

DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO

Total mark of this examination is 100.

This examination is worth 50% of the total assessment.

Answer ANY FIVE questions.

Any form of cheating or attempt to cheat is a serious offence which may lead to dismissal.

Electronics ECE 1312 / ECE 1231

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Q.1 [20 marks]

(a)

(b)

(c)

Calculate the majority and minority carrier concentrations in silicon at

T = 300 K. Assume, ni = 1.51010

cm-3

for Silicon. (6 marks)

(i) Na = 1017

cm-3

(ii) Nd = 51015

cm-3

Describe the difference between a clipper and a clamper circuits. (4 marks)

A diode circuit is shown in Fig. 1(c). Assume that the circuit and diode

parameters are , and

. (10 marks)

(i) Perform DC analysis and calculate VO and ID.

(ii) Using AC analysis, calculate the diodes forward resistance, rf, vo and id.

(iii) Calculate the total instantaneous values of (combined values of DC and AC

components) and .

Fig. 1(c)

Q.2 [20 marks]

(a) A simple half-wave rectifier battery charger circuit is shown in Fig. 2(a). Assume

that battery voltage , R = 100 , and V.

Determine the peak diode current and maximum reverse-bias diode voltage.

(6 marks)

Fig. 2(a)


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(b) Fig. 2(b) shows a multiple diode circuit. If each diode cut-in voltage

is , determine the diode current ID1 and the output voltage .

(7 marks)

Fig. 2(b)

(c) A full-wave bridge rectifier circuit is shown in Fig. 2(c). Determine the peak

output voltage and peak current in the load . Assume each diode cut-in voltage

is and diode forward resistance is . (7 marks)

Fig. 2(c)


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Q.3 [20 marks]

(a) The voltage transfer characteristic and its BJT circuit are shown in Fig. 3(a).

Assume VBE(on) = 0.7 V, VCE(sat) = 0.2 V and = 120.

(i) Find the value of the resistor, RB using VI = 1.9 V (6 marks)

(ii) Sketch the output load line for the circuit. (6 marks)

RB

Fig. 3(a)

(b) For the biasing circuit shown in Fig. 3(b), RB = 250 k, RC = 5 k and VCC = 10 V. Assume that VBE(on) = 0.7 V and = 30, calculate VB, IBQ, ICQ, VC and VCEQ. (8 marks)

Fig. 3(b)


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Q.4 [20 marks]

(a) For the circuit shown in Fig. 4(a), the transistor parameters are = 110,

VBE(on) = 0.7 V, ICQ = 0.2 mA and VCEQ = 3.2 V. Assume RE = 21 k,

RC = 13 k and ro = .

(i) Calculate the small-signal transistor parameters, r and gm. (4 marks)

(ii) Draw the small-signal equivalent circuit. (2 marks)

(iii) Find the small-signal voltage gain Av. (4 marks)

Fig. 4(a)

(b) Draw the small-signal equivalent circuit for the common collector circuit in

Fig. 4(b). Given that ICQ = 1.0 mA, ro = , VBE(on) = 0.7 V and = 100,

calculate the output resistance, Ro and input resistance, Rin of the circuit.

(10 marks)

Fig. 4(b)


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Q.5 [20 marks]

(a) State two (2) differences between a MOSFET and a BJT. (4 marks)

(b) Fig. 5(b) shows a NMOS circuit with parameters VTN = 0.6 V and Kn = 0.2 mA/V

2. Determine VS and VD. Sketch the load line and show the

Q-point. (5 marks)

Fig. 5(b)

(c) A common-source amplifier is shown in Fig. 5(c), where VTP = -1.5 V,

Kp= 2mA/V2, = 0.01 V-1, RD = 2 k and IQ = 2.6 mA.

(i) Draw the small-signal equivalent circuit and calculate gm and ro. (5 marks)

(ii) Determine the voltage gain, Av = vo/vi, for RL = 20 k and for RL = . (6 marks)

Fig. 5(c)


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Q.6 [20 marks]

(a) Sketch the typical I-V characteristics and indicate the nonsaturation and saturation regions for an n-channel MOSFET at various values of VGS (VGS3 > VGS2 > VGS1).

Also show the pinch-off points on the plotted curves. (6 marks)

(b) Fig. 6 (b) shows an n-channel MOSFET logic gate. (i) Draw the corresponding truth table of the logic gate. (3 marks) (ii) Identify the function of the circuit. (AND/OR/NOR/NAND gate) (1 marks)

Fig. 6(b)

(c) An op-amp inverting amplifier circuit is shown in Fig. 6(c). (10 marks)

(i) Show that the close-loop voltage gain of the inverting amplifier, Av = - R2/R1. (ii) Determine the values of R1 and R2, if the gain Av = -8, the current in the

feedback resistor is 10 A when the output voltage is 5.0 V.

Fig. 6(c)


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Useful equations for MOSFET:

where

Useful equations for BJT:

Useful equation for PN junction:

rg

I

Vr

V

Ig

m

CQ

T

T

CQ

m

CQ

Ao

I

Vr

)1( TD

V

v

sD eII

2TNGSnD VVKI

]2[ 2DSDSTNGSnD VVVVKI

CQ

Ao

I

Vr

1AV

DQnm IKg 2

]2[ 2SDSDTPSGpD VVVVKI

2TPSGPD VVKI

iium electronics ece 1312/ece 1231 final exam sem 1 (2012- 2013)

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