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Posted By: Sra1 Member Level: Diamond Posted Date: 27 May 2008
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2007 Jawaharlal Nehru Technological University B.Tech Mechanical Engineering SEMI CONDUCTOR DEVICES AND CIRCUITS (Supplimentary Examinations, Aug/Sep 2007) Question paper
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) What happens to an electron when it is exposed to parallel electric and mag-
netic fields, explain in detail?
(b) Explain the measurement of frequency, with the help of Lissajous pattern?
[8+8]
2. (a) Explain how n-type and p-type semi-conductors are formed? Explain the
concept of hole.
(b) The leakage current in pn junction Germanium diode is 10 µA at room tem-
perature 3000K. Calculate the change in temperature required so that the
leakage current may rise to 40 µA. [8+8]
3. (a) Draw the circuit diagram of Half Wave Rectifier with inductor filter and ex-
plain its operation.
(b) Prove that the RMS component of AC voltage of Half Wave Rectifier is
VR,RMS = Vm
2
pp2
- 4. [8+8]
4. (a) Draw the symbol, neat construction of LED and explain its working?
(b) What are the applications of LED? Explain? [10+6]
5. (a) Explain the need and significance of biasing of transistor (BJT) circuits. Dis-
cuss different types of bias arrangements used in Transistor amplifier circuits.
(b) Define the stability factors, S' and S''. [10+6]
6. (a) Write a short notes on multistage amplifiers.
(b) Draw the equivalent circuit of Two stage RC coupled CE amplifier in the Mid
frequency range, high frequency range and low frequency range. [4+12]
7. (a) Write the advantages and disadvantages of negative feedback and explain .
(b) How does negative feedback reduce distortion in an amplifier
(c) An amplifier has a voltage gain of 200, before negative feedback is applied.
When negative feedback with ß=0.25 is applied, the normal gain changes by
10%. Find the percentage change in the overall gain. [8+4+4]
8. (a) Draw the circuit for Colpitt’s oscillator and obtain the expression for the
frequency of oscillations fo. [16]
(b) Discuss the factors that effect the frequency stability of oscillators. [10+6]
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