Discrete Electronic Circuits - May 2013

Electronics Engineering (Semester 4)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer any four of the following:-

1 (a) Differentiate between direct coupled amplifier and R-C coupled amplifier.(5 marks) 1 (b) Differentiate between small signal amplifier and power amplifier.(5 marks) 1 (c) Explain why constant current source is used in differential amplifier?(5 marks) 1 (d) Give criterion of sustained sinewave oscillations and explain how oscillations start and stabilize in oscillator circuit.(5 marks) 1 (e) Give important features of CASCODE amplifier.(5 marks) 2 Design a two stage RC coupled amplifier for following requirements:
F_L < 20Hz. A_v ~ 1500
S_Ico < 10. R_i > 10kΩ
V_cc= 12 V
Select transistor from the table at the end of question paper. (20 marks) 3 (a) Explain how high frequency response of one stage RC coupled JFET CS type of amplifier can be determined. (10 marks) 3 (b) For the differential amplifier shown in figure, determine:
(i) Q-point of transistors.
(ii) Differential voltage gain (Ad)(10 marks) 4 (a) List Different types of negative feedback, give their stability ratios, effect of feedback on input and on output resistance. (10 marks) 4 (b) For the amplifier shown in figure, determine -
(i) Type of feedback
(ii) Stability Ratio
(iii) A_Vf - Voltage gain with feedback
(10 marks) 5 (a) Design a class A transformer coupled power amplifier to obtain load resistance of 10Ω. V_cc = 12V d.c.(10 marks) 5 (b) Draw the circuit diagram of Wein Bridge Oscillator and explain its working.(10 marks) 6 (a) Discuss problems encountered in multistage direct coupled amplifiers and how to take care of these problems? (10 marks) 6 (b) For power amplifier dissipation of 25 Watts design a heat sink if:-
θ_(j-c)=1 ° C/W, θ_(C-HS)=0.5° C/W
T_jmax=125 °C, T_ambient=30°C.(10 marks)

Write short notes on any three:-

7 (a) Crossover distortion in class B amplifier and how to minimize that.(7 marks) 7 (b) Class C amplifier and its application.(7 marks) 7 (c) Nyquist Stability Criterion.(7 marks) 7 (d) Hartley Oscillator.(7 marks)