Anna University Chennai 2005 B.E Electrical and Electronics Engineering Fourth Semester EC 254 — ELECTRONIC CIRCUITS - Question Paper

B.E./B.Tech. DEGREE EXAMINATION,
Fourth Semester
Electrical and Electronics Engineering
EC 254 — ELECTRONIC CIRCUITS
Time : 3 hours Maximum : 100 marks
ans ALL ques..
PART A — (10 ? two = 20 marks)
1. Name the different kinds of biasing circuits for transistors.
2. What do you understand by class A and class B operations of a transistor?
3. What is the advantage of using FET input stages in differential amplifier?
4. elaborate the applications of tuned amplifiers and classify tuned amplifiers?
5. elaborate the advantages of using negative feed back amplifiers?
6. elaborate the conditions for the sustained oscillations?
7. Draw the integrator circuit and discuss its operation.
8. List the kinds of multivibrators and the function of every kind.
9. describe ripple factor and what is its importance in filter circuits.
10. elaborate polyphase rectifiers?
PART B — (5 ? 16 = 80 marks)
11. (i) Draw the circuit of Wienbridge oscillator and discuss how oscillations are
generated. (10)
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(ii) elaborate the advantages of using crystal oscillators? (4)
(iii) Mention its applications. (2)
12. (a) For the voltage divider bias circuit in fig. 12 a, compute the base voltage
(VB), base current (IB), emitter voltage (VE), emitter current (IE), collector
voltage (VE) and collector to emitter voltage (VCE). The current gain can
vary from 30 to 300. compute the worst case base current.
fig. 12 a
Or
(b) (i) In a Darlington amplifier RE = 100 ?. If 100, 75 one two ? ? ? ? , compute
the overall input impedance. (4)
(ii) Draw the class B push pull emitter follower circuit and discuss its
operation. (12)
13. (a) (i) discuss the subsequent terms of a differential amplifier :
Output offset voltage, Input offset current, Common mode voltage
gain, Differential mode voltage gain and Common mode rejection
ratio. (12)
(ii) If
B1 I and
B2 I through the base resistors of differential amplifier
are I 85 µ A, I 750 µ A
B1 B2 ? ? . compute the input offset current
and Input bias current of the differential amplifier. (4)
Or
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(b) elaborate the kinds of voltage feedback amplifiers? discuss any 1 with
an example. (16)
14. (a) With a neat circuit discuss the working principle of collector coupled
astable multivibrator and draw the necessary waveforms. (16)
Or
(b) (i) Differentiate ranging from clippers and clampers. (2)
(ii) discuss the different kinds of clippers and clampers with examples.
(14)
15. (a) (i) What do you understand by switched mode power supply? (2)
(ii) discuss in detail. (10)
(iii) elaborate the advantages of it? (4)
Or
(b) discuss the procedure for designing a series kind voltage regulator. (16)
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Earning:   Approval pending.