Cochin University of Science and Techology (CUST) 2006-4th Sem B.Tech Electronics and Communications Engineering electronic circuits - Question Paper

MODEL exam APRIL 2006
ELECTRONIC CIRCUITS

Time: 3Hrs


1. a) Briefly define & compare the operating point stabilization techniques with CE
amplifier ckt.

b) Draw the discuss the frequency response of RC coupled amplifier. How does it
differ from that of a direct coupled amplifier.

2. a) discuss the ckt diagram how compensation is accomplished for variation in Vbe
due to temperature variations.

b) describe lower cutoff & upper cut off frequencies, band width reference to frequency
response of an amplifier.

3. a) Draw the equivalent ckt of a common drain JFET amplifier . Derive the expression
for mid frequency voltage gain.

b) discuss the effect of negative feedback on gain & band width.

c) An amplifier with an open loop voltage gain of 1000 delivers 10W of o/p power at
10% 2nd harmonic distortion when the i/p signal is 10mV.If 40 dB negative
series feedback is applied & the o/p power is to remain at 10W determine
i) The needed i/p signal
ii) Percentage 2nd harmonic distortion &
iii) Closed loop voltage gain

OR

4. a) For a JFET bypassed self bias configuration Vp= -2V,Gmo=1.6Ma/V &
Idss=1.65mA.It is desired to bias the ckt at Id=0.8mA using Vdd=24V. presume rd
>>Rd .Find (i) Vgs (ii) Gm (iii) Rs(iv) Rd such that the voltage gain is at lowest 20
dB,with a very large bypass capacitor.

b) elaborate the various kinds of negative feedback encountered in amplifiers ? List
their characteristics.

c) An amplifier has a mid band gain of 1500 & a band width of four MHz . the mid
band gain decreases to 150 when a negative feedback is applied . Determine the
value of feedback factor ?& bandwidth.

5. a) elaborate the advantages of class C amplifier?

b) Derive an expression for the o/p power of a class A large amplifier in terms of
Vmax,Vmin,Imax,Imin.

c) Sketch a topology for a generalized resonator ckt oscillator using impedances
Z1,Z2,Z3. Derive the general formula for oscillator.Under what condition does the
configuration decreases to Colpitt’s & Hartely Oscillator?

OR

6. a) discuss the operation of class B push pull amplifier with the help of a ckt
diagram.In what respect this amplifier configuration is better than class A push pull
amplifier?

b) Draw a RC phase shift oscillator using BJT. discuss its operation . Derive the
expression for the frequency of oscillation.

7. a) Draw a RC phase shift oscillator using BJT. discuss its operation. Derive the
expression for the frequency of oscillation.

b) Draw& discuss the pulse response of high pass RC ckt.?

c) discuss with suitable wave forms ,diode clamper ckt.

d) describe three errors with reference to a sweep signal.

e) Draw & discuss Miller sweep ckt .

OR

8. a) discuss RC integrator & RC differentiator using necessary ckt diagram &
Waveforms

b) What is a UJT? discuss the operation of UJT relaxation oscillation with suitable
ckt diagram & waveforms. Derive the expression for pulse repetition frequency.

9. a) With suitable diagrams discuss the working of a single tuned & double tuned
amplifier.

b) Distinguish b/w broadband amplifiers & narrow band amplifiers.

c) elaborate the advantages of base compensation?

10. a) What is meant by unilaterisation of transistors?

b) What is a tuned amplifier? discuss stagger tuned amplifier.

c) discuss how thw low frequency response can be improved using RC
compensating networks.

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Earning:   Approval pending.