Page 1020 - Basic Electrical Engineering

Figure 14.57 (a) Optocoupler circuit, an LED is driving a phototransistor; (b) optocoupler package
with terminals

14.14 REVIEW QUESTIONS

A. Short Answer Type Questions

1. Distinguish between an intrinsic and extrinsic semiconductor material. What is a p-type
material and an n-type material?
2. Explain how a p–n junction can be used to work as a diode.
3. What is the significance of ‘barrier potential’ in a p–n junction?
4. A reverse-biased p–n junction has a wide depletion region. Explain.
5. What do you mean by forward biasing and reverse biasing of a p–n junction?
6. Sketch the typical voltage/current characteristics for a forward-biased and reverse-biased p–n
junction. Briefly mention the salient points.
7. What is an ideal diode? Draw its characteristic.
8. How is a zener diode different from a conventional diode?
9. Show how a zener diode can be used as a voltage regulator.
10. What are the diode parameters?
11. Show two applications of zener diodes.
12. Explain the operation of a zener diode under forward- and reverse-biased conditions.
13. Explain clearly the difference between acceptor-type and donor-type impurities and state what
types of charge carriers are contributed by them.
14. Distinguish between intrinsic and extrinsic semiconductors. Give examples.
15. Explain the difference between p-type and n-type semiconductor materials. Draw the atomic
structure of silicon and insert an impurity of arsenic in silicon.
16. What are p-type and n-type semiconductors? Draw and explain the V–I characteristic of a p–n
junction diode.
17. Explain for a semiconductor diode the following terms: peak inverse voltage; forward and