8/2/2019 ElectronicCircuitsIINovDec2007

http://slidepdf.com/reader/full/electroniccircuitsiinovdec2007 1/3

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

www.VidyarthiPlus.in

www.VidyarthiPlus.in

8/2/2019 ElectronicCircuitsIINovDec2007

http://slidepdf.com/reader/full/electroniccircuitsiinovdec2007 2/3

(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 )

P 1165

www.VidyarthiPlus.in

www.VidyarthiPlus.in

8/2/2019 ElectronicCircuitsIINovDec2007

http://slidepdf.com/reader/full/electroniccircuitsiinovdec2007 3/3

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

www.VidyarthiPlus.in

www.VidyarthiPlus.in