B.E. (Third semester) EXAMINATION, Feb. 2010
(Common for EC/EE/EX Engg.)
Note: (i) There are five units. Attempt one questions from each unit .
(ii) All question carry equal marks.
(iii) Assume and mention suitable missing data if any .
1. (a) Explain with reference to the zener diode characteristic , Zener voltage , breakdown current and
dynamic impedance . How does the dynamic impedance vary with Zenger current ?
(b) What is PIN diode ? Why it is so called ? What is swept out voltage ? Why is it suitable as a
microwave switch? Is it operated in forward bias or in reverse bias mode ?
2. (a) Explain the working of transistor as an amplifier .
(b) Given hie =2.4 K , hfe =100 =4 × 10-4 and hOE = 25 µS.
Sketch the common emitter equivalent model .
3. (a) Differentiate between positive and negative feedback . How does negative feedback modify the
gain of an amplifier.
(b) Derive the expression for the gain of an amplifier using negative feedback.
4. (a) Draw the circuit of a Wien bridge oscillator . Discuss its working will oscillation take place if bridge
is balanced ?
(b) A class A push pull amplifier is supplied with VCC =50 V. The signal swings the collector voltage
down to Vmin = 10V . The dissipation in both transistors total 40 W. Find the total power and
5. (a) For a monostable multavibrator calculate the input pulse width for the design values of RC = K, RB
=K, C =0.1 µF, VCC = 10V, VBE(sat) = 0.8V.
(b) Draw the circuit diagram of an astable multavibrator , Justify that it is a to stage R-C coupled
amplifier using feedback . How does it give a square wave ?
6. (a) How it transistor used as a clipper ? Draw the circuit diagram and output waveform for sinusoidal
input signal .
(b) Draw the circuit diagram of Darlington amplifier . Give its main characteristics , merits and
7. (a) Why current source is used in conjunction with differential amplifier ? Draw the circuit diagram .
(b) Draw the circuit diagram og log and antilog amplifier circuit using OP-Amp and write the
expression for output voltage.
8. (a) Using 555 timer draw the circuit of monostable multavibrator and find the expression for pulse
(b) Determine the voltage gain of an Op-Amp . instrumentation amplifier.
9. (a) Explain the working principle of a regulated power supply.
(b) Explain , with a neat block diagram of the internal blocks. The working of an I.C. voltage regulator .
10. (a) For a transformer output of 24 V and a filter capacitor of 200 pF, determine the minimum input
voltage when connected to a load drawing 300mA.
(b) Write the principle of voltage regulator . What do you understand by SMPS ?