Electronic Circuits - Dec 2012

Computer Science Engg. (Semester 3)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Explain transistor in its fixed bias mode with relevant expression.(6 marks) 1 (b) With a neat sketch, explain transistor as a switch.(6 marks) 1 (c) For the circuit shown calculate I_B, I_C, V_CE, V_C, V_E, V_B. Assume β=100. (8 marks) 2 (a) Explain the VI characteristics of n-channel JFET and define various conditions.(8 marks) 2 (b) Explain the construction and working of n-channel depletion mode MOSFET.(8 marks) 2 (c) Mention merits and demerits of IGBT.(4 marks) 3 (a) Explain the construction and working of phototransistor and mention its applications.(10 marks) 3 (b) What are optocouplers? Explain the working and characteristics of optocoupler.(10 marks) 4 (a) Derive expression for A_i, Z_i, A_v, Y_o, A_p for a transistor amplifier using h-parameter model.(12 marks) 4 (b) Explain the need for cascading amplifier and with the block diagram, explain two stage cascaded amplifier.(8 marks) 5 (a) Explain different fb amplifier.(8 marks) 5 (b) with the block diagram, explain the negative feedback in small amplifier.(6 marks) 5 (c) An amplifier having a voltage gain of 60dB uses 1/20^th of its output in negative feedback. Calculate the gain with feednack, the percentage change in gain without and with feedback consequent on 50% change in gm.(6 marks) 6 (a) Explain the construction working of RC phase shift oscillator.(8 marks) 6 (b) Find the frequency of the oscillations of a Colpitts oscillator having C₁=150pF, C₂=1.5 nF and L=50μH.(4 marks) 6 (c) With a circuit diagram, explain the working of RC low pass and RC high pass circuits.(8 marks) 7 (a) With a block diagram, explain the working of three terminal voltage regulators.(6 marks) 7 (b) Explain the construction and working of SMPS and mention different types of switching regulators.(8 marks) 7 (c) Define the terms load regulation, line regulation and output resistance for a voltage regulator.(6 marks) 8 (a) Briefly explain characteristics of an ideal op-amp and compare with practical op-amp.(10 marks) 8 (b) With relevant formulas, neat diagram and wave form explain op-amp Schmitt trigger.(10 marks)