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B3D057 Total pages:2
b) Make a distinction between “voltage” feedback and “ரள?” feedback in amplifier

circuits. Discuss the merits in each case and derive expressions for the net output
resistance in each case. (8)
a) Sketch the topology for the generalized resonant circuit oscillator, using impedances
2, 22 and 73. Derive the expression for the frequency of oscillation. Under what
conditions does the configuration reduce to Colpitts oscillator? (10)

b) Derive the equation which shows that the sensitivity of an amplifier reduces by
applying negative feedback to the circuit. (5)
a) Deduce the high frequency equivalent circuit of a potential divider bias CE amplifier
circuit. Derive the expression for the CE short circuit current gain as a function of

frequency. Explain with frequency response characteristics diagram, the

relationship between fp and fr. (12)
b) Draw the circuit of a cascode amplifier and explain its properties. (3)
PARTC

Question is 7 COMPULSORY and Answer EITHER Question 8 OR Question 9 Each
Full Question Carries 20 marks.

a) With neat circuit diagram and necessary waveforms, explain how a transistorized
astable multivibrator is working as a free running oscillator. Derive the expression for
the frequency. Show in the circuit diagram, how you can eliminate the rounding of the
collector waveform and make the edges sharp? (12)
b) An N-channel E-MOSFET used in a potential divider bias CS amplifier has ന
4mA at ५65७0 8V, Vast = 4५, ஜு 2 mS. Calculate values of (i) Vas, (ii) Vos, (iii)
Ip and (iv) output Voltage, if Ri=60kQ, R2 = 40kQ, Rp = 6kQ, ‏م۷‎ = 15४ and the
ac input signal = 80mV. (8)
a) Using fictitious generator block diagram, show how a Bootstrap generator can
produce linear sweep voltage by constant current charging. Draw a transistorized
circuit and waveforms to explain the Bootstrap action to generate linear sweep. (12)
b) A Class 8 push-pull power amplifier is supplied with Vcc = 50V. The signal swings

the collector voltage down to Vmin = 5४. The total dissipation in both transistors is

40W. Calculate the total output power and conversion efficiency. (8)
a) Draw the circuit of a series pass voltage regulator which uses a feedback. Explain its
working when the input voltage as well as load current varies. Design your circuit
to deliver 6V, 100mA maximum load current. (12)
b) Draw the circuit of a Drain feedback bias circuit for E- MOSFET. Explain its

working and properties. (8)
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