Question Paper: Electronic Circuits : Question Paper Jun 2013 - Computer Science Engg. (Semester 3) | Visveswaraya Technological University (VTU)
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## Electronic Circuits - Jun 2013

### 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) With neat figures, explain the construction and operational principle of an Uni Junction Transistor (UJT).(10 marks) 1 (b) Find the values of resistors RB, RC, RE and the transistor gain β, for the circuit shown in Fig.Q1(b). Given that, IB=40 μA, IC=4 mA, VE=2V, VCE=12 V and supply voltage VCC=15 V. Assume that the transistor used in the circuit is a silicon transistor. (5 marks) 1 (c) Explain thermal runaway as referred to transistor.(5 marks) 2 (a) What are the differences between JFET's and MOSFET's?(5 marks) 2 (b) With the help of neat figures, explain the construction and characteristics of N-channel depletion MOSFET.(10 marks) 2 (c) Fig.Q2(c) shows a biasing configuration using DE-MOSFET. Given that the saturation drain current is 8 mA and the pinch off voltage is - 2 V. Determine the value of gate-source voltage, drain current and the drain source voltage. (5 marks) 3 (a) Define the following terms:
(i) Responsivity (R)
(ii) Noise equivalent power (NEP)
(iii) Detectivity
(iv) Quantum efficiency
(v) Response time.
(5 marks)
3 (b) What is photo transistor? Draw the schematic symbol of a phototransistor. Explain the V-I characteristics of photo transistor.(5 marks) 3 (c) Explain different modes of operation of an LCD display.(10 marks) 4 (a) Draw the generalized h-parameter model of a transistor based amplifier and derive the expression for:
(i) Current gain
(ii) Input impedance
(iii) Voltage gain