B.E. (Third semester) EXAMINATION, DEC, 2004
(Common for EC/EE/IP Engg.)
Note: Attempt any five questions. All question carry equal marks. Assume any data missing.
1. (a) Explain the V-1 characteristics of zener diode and explain its working as a voltage regulator .
(b) Define the pinch off voltage V p. Sketch the depletion region before and after pinch off. How does
FET behaves in the region before and after pinch off ?
2. (a) Distinguish between positive feedback and negative feedback . List the characteristics of an
amplifier that get modified by negative feedback.
(b) Explain the Wien’s bridge oscillator using BJT. For this circuit calculate the frequency of
3. (a) Draw a self bias circuit for a transistor . Why these circuit has an improvement on fixed bias circuit
? How the load line is drawn in self bias circuit.
(b) Determine the d.c. bias voltage V CE And the current IC From the circuit given below :
4. (a) Give the characteristics of class- A power amplifier . Deduce the expressions where necessary.
(b) A transformer coupled class – A amplifier , maximum collector current charge is 100 mA ; VCC =10 .
Find the power transferred to 4 ohm speaker load if it is
(i) Direct coupled (ii) Transformer coupled (Find the turn ratio of transformer)
5. (a) Draw the circuit of Bitable multavibrator . Explain its working.
(b) What is voltage comparator ? How to generate a saw-tooth using op-amps ?
6. (a) Explain the operation of a transistorized differential amplifier . Show the input bias currents clearly
and how input offset current can be minimized ?
(b) What are the characteristics of an ideal Op-Amp . Derive the formulas for inverting and non-verging
7. (a) Explain V-1 characteristics of SCR . What is meant by Gate on and Off times ?
(b) Explain the operation and application of convertor . invertors and choppers circuits.
8. Write short notes on any three of the following :
(a) Varactor diode
© Hartley oscillator
(d) Instrument amplifier
(e) Power MOSFET and IGBT