Discrete Electronic Circuits - May 2012

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) Explain differential amplifier with active load.(5 marks) 1 (b) What is cross-over distortion in class B power amplifier? Explain with waveform?(5 marks) 1 (c) State advantages of negative feedback on performance of amplifier.(5 marks) 1 (d) For the circuit given below calculate dc bias voltages V_B1, V_B2 and V_C2.(5 marks) 1 (e) For the circuit given below determine the 3dB frequencies and the bandwidth.(5 marks) 2 Design a two stage RC coupled amplifier for following requirements:
F_L better than 15 Hz. A_v ≥ 1500
S_Ic < 8, R_i ≥ 1MΩ
V_cc=6 V
Select transistor from the table at the end of question paper. (20 marks) 3 (a) Explain Class B Push Pull amplifier and derive the expression for maximum efficiency.(10 marks) 3 (b) For the given differential amplifier determine dc voltages, currents and single ended output voltage V₀₁. (10 marks) 4 (a) For Class B amplifier with V_cc=20V driving an 16Ω, determine:-
(i) Maximum input power.
(ii) Maximum output power.
(iii) Maximum circuit efficiency.
(iv) Transistor dissipation.(10 marks) 4 (b) Explain high frequency analysis of a BJT amplifier. Derive necessary expressions.(10 marks) 5 (a) Draw the circuit diagram of Wein Bridge Oscillator and explain its working. Derive the necessary equation for frequency of oscillations and for sustaining oscillations. (10 marks) 5 (b) For the following circuit, determine
A, β, A_f, Z_if, Z_of, and A_vf.(10 marks) 6 (a) Determine the lower cut-off frequency for the following network. (10 marks) 6 (b) For a current series negative feedback amplifier, derive the expression for the input and output resistances with feedback and comment on the result. (10 marks)

Write short notes on any three:-

7 (a) Heat sink and its design steps.(7 marks) 7 (b) CMRR improvement in differential amplifier.(7 marks) 7 (c) Nyquist stability criterion.(7 marks) 7 (d) Crystal Oscillator.(7 marks)