GTU Electronic Devices and Circuits - December 2014 Exam Question Paper

GTU Electronics and Communication Engineering (Semester 3)
Electronic Devices and Circuits
December 2014

Total marks: --
Total time: --

INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Define the following terms:
(1) Doping
(2) Clipper
(3) Diffusion
(4) Static Resistance
(5) Drift current
(6) Bulk Resistance
(7) Barrier Potential

7 M

1 (b) Give the comparison between half wave rectifier, full wave rectifier and bridge rectifier with the help of following points:
a) No of diodes
b) Transformer necessity
c) PIV ratings
d) Average dc current e) Average dc voltage
f) rms current
g) Ripple factor
h) Rectifier efficiency

7 M

2 (a) Draw and explain the input and output characteristics of common emitter Configuration.

7 M

Answer any one question from Q2 (b) & Q2 (c)

2 (b) What is voltage multiplier? Draw and explain full wave voltage doubler.

7 M

2 (c) Describe the construction, the symbol, V-I characteristics and application of varactor diode.

7 M

Answer any two question from Q3 (a), (b) & Q3 (c), (d)

3 (a) What is multistage amplifier? Explain in detail with neat diagram two stages RC coupled amplifier.

7 M

3 (b) What is the need of biasing the transistor? Describe the voltage divider bias circuit.

7 M

3 (c) What is voltage regulation? Explain the working of two transistor regulator.

7 M

3 (d) Design a fixed bias circuit biased using NPN transistor which has ?=150.The dc biasing point at V_CE =5V and I_C=5mA. Supply voltage (V_CC) is 10V.

7 M

Answer any two question from Q4 (a), (b) & Q4 (c), (b)

4 (a) Define positive and negative feedback. Also derive the expression of transfer gain with negative feedback with the use of block diagram.

7 M

4 (b) Compare :(1) BJT with FET (2) Small signal amplifier and large signal amplifier.

7 M

4 (c) Derive input resistance for voltage shunt feedback amplifier and current series feedback amplifier.

7 M

4 (d) Classify amplifiers based on position of Q-point. Show the efficiency of class-A transformer coupled amplifier is 50%.

7 M

Answer any two question from Q5(a), (b) & Q5 (c), (d)

5 (a) Draw and explain the construction, operation and drain characteristic of N-channel JFET.

7 M

5 (b) Explain the working of emitter follower. Draw the ac equivalent circuit and determine the AC emitter resistance, voltage gain and input impedance.

7 M

5 (c) An amplifier gain changes by ±10% without any feedback. Using negative feedback the amplifier is to be modified to yield a gain of 100 with ±0.1% variation. Find the required open loop gain of the amplifier and the amount of negative feedback.

7 M

5 (d) What is MOSFET? Compare depletion type and enhancement type MOSFET.

7 M

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