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

15. Draw sketches to show the construction, equivalent circuit and characteristics of a TRIAC. Identify all important voltage and current levels on the characteristics and discuss the operation of the device.
16. Draw the typical characteristics of a DIAC. discuss the DIAC operation and sketch the 2 circuit symbols used for the device.
17. (a) Compare the properties of BJT and FET
(b) discuss the terms intrinsic stand off ratio, negative resistance region, peak
voltage and valley voltage.






&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

UNIT II

TWO MARK ques.

1. Name the opto electronic device that
(i) emits light (ii) modifies light
2. Why P-type layer is kept uppermost in a LED?
3. Name the semiconductor materials used in LED and the color of light emitted by them.
4. Draw the graphic symbol of LED and photo diode.
5. State the principle of operation of LED.
6. Write down the typical values of forward voltage drop, reverse break down voltage and power dissipation in a LED.
7. Explain why a gold film is applied to the bottom of the substrate in a LED?
8. Justify why an ordinary PN junction diode is connected in series with a LED in a few LED circuits.
9. Draw the seven-segment LED display in common anode & common cathode configurations.
10. List a few of the applications of LED.
11. What are the merits of LED over conventional lamp
12. What are the properties of liquid crystal material?
13. Explain why an energized liquid crystal cell appears dark.
14. Explain the principle of reflective kind LCD.
15. Explain the principle of transmittive kind LCD.
16. What is the maximum numerical value that can be displayed by
(i) three and half digit seven segment LED display
(ii) five and half digit seven segment LED display.
17. Explain why LCD consumes very small volumes of energy compared with LED?
18. Explain why LCD requires a AC voltage supply?
19. List the applications of LCD.
20. What is the advantage of LED over LCD?
21. Which device has faster response time LED or LCD? discuss.
22. An LED requires external interface circuit when driven from an IC. discuss why?
23. Explain the principle of operation of photo diode.
24. A photo diode is reverse biased by a two volt dc supply and it is obtained that a leakage current of 13µA flows when the illumination level is 5mW/cm2. compute the device resistance.

Earning:   Approval pending.