electroniccircuitsiinovdec2007
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Reg. No. :
P 1165
B.E./B.Tech.DEGREE EXAMINATION. NOVEMBER/DECEMBER2007.
Fourth Semester
Electronics and CommunicationEngineering
EC 241- ELECTRONIC CIRCUITS_ II
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PARTA- (10x2=20marks )
1. Define negative and positive feedback.
2. DefineLoopgain.
3. State Barkhausen's criterion for oscillatron.
4. Crystal Oscillators possess igh degreeof frequency stability- Justify.
5. Define'Q'of tank circuit.
6. What is Neutralisation.
7. What is the other name of Astable Multivibrator?
8. State the use of Schmitt trigger.
9. What is BlockingOscillator.
10. State any two applicationsof Pulse ransformers.
PARTB- (5x16=80marks )
11. (a) Draw the circuit of a current series feedback amplifier and explain.
Derive expressionsor input and output impedence.How does t improve
the stabilitv of the amplifier. (16)
Or
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(i) Draw the block diagrams of the four possible feedback topologies
and explain. (8)
(ii) Prove that the bandwidth of the amplifier increaseswith negative
feedback. (8 )
(i) What type of feedback s applied for oscillators? (2)
(ii) Draw the circuit diagram of wein bridge oscillator. Explain the
needfor providing both positive and negative feedback. (7)
(iii) Draw the circuit of RC phase shift oscillator. With R = 6kf2,
C = 1500PF and Rc = 18 kQ, obtain ts operating requency. (7 )
Or
(b) Draw the circuit of a Colpitts Oscillator. Derive expressionsor frequency
of osciliation and condition for oscillation. (16)
13. (a) Draw the circuit of a Single tuned amplifier. Draw its frequency
response. Using small signal equivalent circuit derive expressions for
(b)
(a)2
gain at resonance and 3 dB bandwidth. (16)
(8)
(8)
(b) Write short notes on :
(i ) HazeltineNeutralisation.
(ii) Class C Tuned amplifier.
14. (a) Draw and explain the circuit of astable multivibrator and hence draw the
waveforms at salient points. Derive expressions for frequency of
osciliation. (16)
Or
ft) (i) Draw and explain the circuit of a Monostable multivibrator with
suitable triggering arrangements. Give the waveforms at different
modes. (10)
Derive an expression fo r th e pulse width of a Monostable
multivibrator. (4)
State any two applications of Monostable multivibrator. (2)
( i i )
( i i i )
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15. (a) Explain with circuit diagram and waveforms the Transistor voltage time
basegenerator that uses Bootstrapping. (16)
Or
(b) Explain with suitable diagrams and waveforms the working of a UJT
relaxation oscillator. Also derive its frequency of oscillation. (16)
P 1r.65
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