SKR Engineering College 2007 B.E Electrical and Electronics Engineering EC 1261 – ELECTRONIC CIRCUITS - Question Paper

SKR ENGINEERING COLLEGE
POONAMALLI, CHENNAI – 602003
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGG
IV SEM - ELECTRICAL & ELECTRONICS ENGG
EC 1261 – ELECTRONIC CIRCUITS

MODEL exam
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Date: 12.4.07 Maximum: 100 Marks
Duration: three Hrs

PART: A (10×2 = 20)

1. Draw the small signal equivalent (hybrid equivalent) circuit of CE amplifier along with amplifier circuit.
2. A fixed bias transistor circuit has operating point (6 V, 1mA) with VCC = 10 and hfe = 100. compute the collector resistance Rc and base bias resistance Rs.
3. What is the need for differential amplifier?
4. Draw the circuit diagram of a stagger tuned amplifier.
5. With block diagram of current series feedback topology, find expression for Rif.
6. What kind of feedback is used in oscillator? Why?
7. Draw a slicer circuit and discuss its slicing operation.
8. Sketch the output waveform of a Schmitt trigger circuit for sine wave input of 12V peak to peak if UTP = 5V and LTP = 3V.
9. Define ripple factor and what is its importance in filter circuits.
10. Define line regulation and load regulation.

PART: B (5×16 = 80)

11. Define Class B operation with neat circuit. discuss complementary symmetry Class-B power amplifier. Derive expression for its efficiency. elaborate its merits and demerits? (16)
(OR)

12. a) Prove that self-bias is better bias compared to collector to base bias. (8)
b) Draw a Darlington amplifier circuit and mention its advantages. (6)
c) describe power amplifier and mention its kinds. (2)

13. Derive the expression for the differential and avg. voltage gain of a dual input
dual output differential amplifier and discuss the modification done to improve its
CMRR. (16).
(OR)

14.Draw the circuit diagram of a single tuned amplifier and discuss its operation.
What other tunings are practically applied and draw the circuit for every 1 of
them? What improvements are achieved as a result? (16)
15. Draw the circuit diagram of an oscillator, which produces audio frequencies using a two-stage amplifier. discuss its operation. Derive expression for its frequency of oscillation. (16)
(OR)

16. discuss the characteristics (Effect) of negative feedback amplifiers. (16)

17. describe one-shot multivibrator. discuss the operation of one-shot multivibrator with charging and discharging constant. Also derive its time period and frequency of oscillation. (16)
(OR)

18. discuss the operation and of Schmitt trigger circuit and design computation
(16)

19. a) define the working of full wave rectifier with LC filter and derive the
expression for ripple factor. (12)
b) compute the inductance to be used in L filter of FWR at 60Hz to give Dc
output with ripple of 4% at 300 ohms load.(4)

(OR)
20. a) discuss the operation of transistorized series regulator (5)
b) Design simple Zener regulator with subsequent specification.
Vo = 20V, Vin = (20 – 30) V, IL (max) = 50mA.(7)
c) discuss the operation of Zener shunt regulator. (4)

Earning:   Approval pending.