SRM University 2007 B.Tech Information Technology ELECTRONIC DEVICES AND CIRCUITS - Question Paper

(ii) Discuss the properties of ideal and practical opamp.
14. Write short notes on record playback and tone control.









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UNIT IV

TWOMARKS

1. What is oscillator?
2. List the various kinds of oscillator available.
3. State barkhausen criteria
4. What is the disadvantage of LC and RC oscillators?
5. What is the main difference ranging from an amplifier and an oscillator?
6. Explain what you mean by sinusoidal oscillator and relaxation oscillator.
7. State the principle behind sinusoidal oscillators.
8. Define frequency stability of an oscillator and list the factors that affect frequency stability.
9. For a phase shift oscillator justify the name.
10. Draw the feedback circuit of a RC phase shift oscillator.
11. Explain why in an opamp based RC phase shift oscillator the amplifier gain is always slightly greater than 29.
12. In an opamp based RC phase shift oscillator what is the minimum gain that should be maintained why?
13. Write down the condition when the phase shift of an opamp based RC phase shift oscillator equals 180 degrees. Also write down the expression for its frequency of oscillation.
14. Write down the expressions for frequency of oscillation and hfe(min) for an BJT phase shift oscillator.
15. What is the minimum value of hfe needed for a BJT phase shift oscillator if Rc=R ?
16. Explain why collector resistance Rc must be partially adjustable in BJT phase shift oscillator/
17. What are the merits and demerits of the phase shift oscillator?
18. Draw the feedback circuit of a wein bridge oscillator.
19. Explain the principle of wein bridge oscillator.
20. Justify why wein bridge in the wein bridge oscillator must be kept at balance?
21. Write down the condition for balance of the bridge in wein bridge oscillator circuit. Also write the expression for frequency of oscillation.
22. What is a comparator?
23. Mention 2 important characteristics of a comparator.
24. List any 4 applications of a comparator.
25. When does an opamp act as a switch?
26. Draw the schematic of a non-inverting comparator.
27. Draw the schematic of an inverting comparator.
28. Discuss the use of clamp diodes in opamp based comparator circuits.
29. What is zero crossing detector?
30. Show how a zero crossing detector detects the direction in which input signal crosses zero volts.
31. Draw the circuit diagram of an opamp based Zero crossing detector.
32. Draw the input output waveforms of an opamp zero crossing detector.

Earning:   Approval pending.