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Posted By: bhavani Member Level: Bronze Posted Date: 03 Jun 2008
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2008 Anna University B.E Computer Science MODEL EC1X11 Question paper
MODEL QUESTION PAPER
B.E/B.TECH DEGREE EXAMINATION
First Year (CSE&IT) – Annual pattern
EC1X11-ELECTRON DEVICES AND CIRCUITS
Answer all questions
Time: 3hrs Max marks: 100
PART-A (10X2=20 Marks)
1. Name two donar impurities.
2. What is meant by diffusion current?
3. Derive the expression for common emitter current gain in terms of common base one.
4. What is known as pinch-off voltage in FET?
5. Define positive feedback and negative feedback.
6. What should be the minimum voltage gain in a phase shift oscillator so as to maintain
Oscillations? Why?
7. What is an LCD? What are its advantages?
8. Sketch the V-I characteristics of SCR.
9. Find Vo in the circuit shown.
10. Why integrators are preferred over differentiators?
PART-B (5X16=80 Marks)
11.(A)(I) Briefly explain the two types of extrinsic semiconductors.
(ii) Derive the expression for diffusion capacitance in PN junction diode.
(b)(I) Explain the principle of operation of HWR and derive an expression for it s ripple factor and efficiency.
(ii) Draw the zener diode characteristics and explain its nature.
12.(a)(I) Explain the construction and operation of n-channel JFET.
(ii) Sketch the typical family of drain characteristics for an n-channel JFET with various levels of
Vgs.
(b)(I) With neat diagram explain DC load line and AC load line.
13.(a)(I) Explain the working of common collector amplifier. List its characteristics.
(b)(I) An amplifier has a voltage gain of 200. The feedback ratio is 0.04. Calculate(I) the voltage
gain with feedback (ii) the output voltage of the feedback amplifier for an input voltage of
30mV (iii) the feedback factor and (IV) the feedback voltage.
(ii) Explain the working of colpitts oscillator. Derive the expression for frequency of oscillation.
14.(a)(I) Explain in detail about the Triac construction and operation and characteristics.
(ii) Explain the construction and operation of LED.
(b) Write short notes on (I) Optoisolator (ii) Solar cell.
15.(a)(I) Draw the circuit of differentiator using operational amplifier and explain with relevant
derivations that the circuit acts as a differentiator.
(ii) Explain the application of operational amplifier as a voltage to current converter.
(b)(I) Design a second order Butterworth low pass filter using operational amplifier with midband gain of 4 and a cut-off frequency of 1 KHz.
(ii) Explain the working of astable multivibrator using op-amp.
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