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VTU Computer Science (Semester 3)
Analog and Digital Electronics
May 2016
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1(a) With the help of common ' emitter amplifier configuration, explain the criteria for selection of a suitable operating point and the factors affecting its stability.
8 M
1(b) Fig. Q1(b)(i) shows the transistor as an inverting switch with the desired output waveform for the given input waveform as shown in fig. Q1(b)(ii). Find the value of Vcc, Rc and RB given that β=80, Ic(sat)=10mA, the output voltage Vout when the transistor is off is 12V, VBE=0.7V.  8 M
1(c) Explain the gate triggering characteristics of an SCR.
4 M

2(a) Draw and explain the working of D-MOSFET with the help of drain current and transconductance curve. When the voltage is applied to the gate of a P-channel D-MOSFET, does the current flow depleted or enhanced?
12 M
2(b) Fig.Q2(b) shows a circuit using E ' MOSFET given that the threshold voltage for the MOSFET is 2V and Id(on)=6mA for VGS(on)=5V, determine the volume of the operating point. 8 M

3(a) What are photodiodes? Explain with VI characteristics.
5 M
3(b) Determine the cut-off wave length for silicon and germanium photodiodes, given that their Bandgap energies are 1.1 ev and 0.72 ev, respectively, at 25°C. How will the cut off wave length change when the operating temperature change form 25°C to 200°C?
5 M
Write short note on:
3(c)(i) Cathode ray tube display
5 M
3(c)(ii) Emerging display technologies.
10 M

4(a) Explain how the h-parameters are determined by making use of transistor's input and output characteristics.
10 M
4(b) Carryout the analysis of a transistor amplifier operating in common emitter fixed bias configuration with suitable derivations.
10 M

5(a) Distinguish between class A, class B, class C, class D, class AB amplifiers interms of conduction angle, operating region, application and efficiency.
5 M
5(b) Explain all four feedback topologies with appropriate circuit diagrams.
10 M
5(c) An amplifier has a open ' loop voltage gain Av=1000 ± 100. It is required to have an amplifier whose voltage gain varies by no more than ±0.1%.
i) Find the value of feedback factor β
ii) Find gain with feedback.
5 M

6(a) Explain Barkhausen criteria with suitable circuit diagrams essential conditions.
5 M
6(b) Explain with a neat connection diagram and waveforms how IC555 timer is used as the astable multivibrator.
8 M
6(c) A step input of amplitude 8 volts is applied to a RC low ' pass circuit shown in fig. Q.6(c)(i) and Fig.Q.6(c)(ii) below. Determine the output voltage at end of : i) 2m/sec ii) 5m/sec ii) Find upper cut-off frequency fw and rise time tr. 7 M

7(a) Write a note on 3 terminal voltage regulator.
5 M
7(b) Determine the regulated output voltage for LM 317 voltage regulator shown in Fig.Q.7(b). 5 M
7(c) What are switching regulators? Describe the basic topology of Boost regulator.
10 M

8(a) Differentiate ideal Op-Amp and practical Op-Amps.
5 M
8(b) Discuss performance parameters of operational amplifiers.
10 M
8(c) Explain Op-Amp as peak detector circuit.
5 M

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