nr10205 semiconductor devices circuits set1

Code No: NR10205 NR I B.Tech Supplementary Examinations, Aug/Sep 2006 SEMICONDUCTOR DEVICES & CIRCUITS ( Common to Electrical & Electronic Engineering, Electronics & Communication Engineering, Computer Science & Engineering, Electronics & Instrumentation Engineering, Bio-Medical Engineering, Information Technology, Electronics & Control Engineering, Computer Science & Systems Engineering, Electronics & Telematics and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) Draw the schematic diagram of a CRT and explain about the various sections and the materials used. (b) In a CRT, the electrons emitted are accelerated by a potential of 500V. The length of the deflecting plates is = 1.3cm. Distance between the deflecting plates in 0.5cm. The distance between the centre of the deflecting plates and the screen is 20cm. Determine the value of electrostatic deflection sensitivity S E . [10+6] 2. (a) Explain qualitatively the V-I characteristics of a tunnel diode. (b) Calculate the dynamic forward and reverse resistance of a p-n junction diode when the applied voltage in 0.24V. Assume Germanium diode. I 0 =2μA. T = 300 o K. [8+8] 3. (a) Draw the circuit of a p - n - p BJT in C.E Configuration and explain about the static Input and Output characteristics. (b) For a given transistor (BJT), α =0.96, I co =2μA I Eo =2.5μA. When the collector is open circuited, the forward current is 3 μA. Calculate the junction voltages V c and V E . [8+8] 4. (a) Draw the circuit for a single stage R-C coupled amplifier and qualitatively explain about the frequency response. (b) Give the specification of JFET and MOSFET. [10+6] 5. (a) Derive the expression for input resistance R i with negative shunt feed back. (b) Show that with negative feedback stability of the circuit improves. (c) What are the advantages and disadvantages of +ve feed back. [6+5+5] 6. (a) Draw the circuit for the Hartley oscillator and explain its principle of working. (b) Explain the concept of generation of sinosoidal oscillations in circuits. What are the Berkauhsen criteria? Explain. [8+8] 7. (a) Compare Direct coupled, R- C coupled and Transformer coupled amplifier circuits in all respects. 1 of 2

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Code No: NR10205 NR

I B.Tech Supplementary Examinations, Aug/Sep 2006SEMICONDUCTOR DEVICES & CIRCUITS

( Common to Electrical & Electronic Engineering, Electronics &Communication Engineering, Computer Science & Engineering, Electronics

& Instrumentation Engineering, Bio-Medical Engineering, InformationTechnology, Electronics & Control Engineering, Computer Science &

Systems Engineering, Electronics & Telematics and Electronics & ComputerEngineering)

Time: 3 hours Max Marks: 80Answer any FIVE Questions

All Questions carry equal marks? ? ? ? ?

1. (a) Draw the schematic diagram of a CRT and explain about the various sectionsand the materials used.

(b) In a CRT, the electrons emitted are accelerated by a potential of 500V. Thelength of the deflecting plates is ` = 1.3cm. Distance between the deflectingplates in 0.5cm. The distance between the centre of the deflecting plates andthe screen is 20cm. Determine the value of electrostatic deflection sensitivitySE . [10+6]

2. (a) Explain qualitatively the V-I characteristics of a tunnel diode.

(b) Calculate the dynamic forward and reverse resistance of a p-n junction diodewhen the applied voltage in 0.24V. Assume Germanium diode. I0 =2A. T =300o K. [8+8]

3. (a) Draw the circuit of a p - n - p BJT in C.E Configuration and explain aboutthe static Input and Output characteristics.

(b) For a given transistor (BJT), = 0.96, Ico = 2A IEo = 2.5A. When thecollector is open circuited, the forward current is 3 A. Calculate the junctionvoltages Vc and VE. [8+8]

4. (a) Draw the circuit for a single stage R-C coupled amplifier and qualitativelyexplain about the frequency response.

(b) Give the specification of JFET and MOSFET. [10+6]

5. (a) Derive the expression for input resistance Riwith negative shunt feed back.

(b) Show that with negative feedback stability of the circuit improves.

(c) What are the advantages and disadvantages of +ve feed back. [6+5+5]

6. (a) Draw the circuit for the Hartley oscillator and explain its principle of working.

(b) Explain the concept of generation of sinosoidal oscillations in circuits. Whatare the Berkauhsen criteria? Explain. [8+8]

7. (a) Compare Direct coupled, R- C coupled and Transformer coupled amplifiercircuits in all respects.

1 of 2
Code No: NR10205 NR

(b) Design a class A transformer coupled amplifier using BJT to give 70 mw ofoutput power. RL = 4 . At the operating point IB = 200A. Vce =15V . Collector dissipation should not exceed 200mw. R

L= 800. Asume

reasonable values wherever necessary. [16]

8. Write notes on any Two:

(a) Wein-Bridge oscillator

(b) Multi stage Amplifiers.

(c) UJT [16]

? ? ? ? ?

2 of 2