Chapter 14 Semiconductor Electronics
1. The band gap at 300K of crystals A, B, C, D is 5.5, 1.2, 0.67 and 0.1 units respectively. Answer the
following questions based on this information.
a) What do you understand by band gap?
b) What is the most common unit to measure band gap?
c) In the above case, which crystal will have the highest electrical conductivity at 300K? Why?
2. Biasing is provided for maintaining proper current flow across a p-n junction.
a) In a biased p-n junction the net flow of holes is from ‘n’ region to ‘p’ region.
b) For the device shown below draw the V -1 characteristics when the potential is applied between
the terminals A and B.
3. Two semiconductor materials A and B shown in the given figure are made by doping germanium
crystal with arsenic and indium respectively. The two are joined end to end and connected to a
battery as shown.
a) Will the junction be forward biased or reverse biased? Justify your answer.
b) Sketch a V-l graph for his arrangement.
4. We are familiar with the semiconductors Silicon and Germanium.
a) With a necessary schematic diagram, briefly explain the characteristics of an intrinsic
semiconductor.
b) Draw the energy bands of a n-type semiconductor.
5. You are given two p-n junction diodes.
a) Mention the name of an electronic circuit which make use of these diodes to convert A.C. current
to continuous D.C. current.
b) Draw the circuit diagram of the above-mentioned circuit.
6. Q 1. In an n-type silicon, which of the following statement is true:
(a) Electrons are the majority carriers, and trivalent atoms are the dopants.
(b) Electrons are minority carriers, and pentavalent atoms are the dopants.
(c) Holes are minority carriers, and pentavalent atoms are the dopants.
(d) Holes are the majority carriers, and trivalent atoms are the dopants.
7. When a forward bias is applied to a p-n junction, it
a. raises the potential barrier.
b. reduces the majority carrier current to zero.
c. potential barrier is reduced.
d. None of the above
8. In half-wave rectification, what is the output frequency if the input frequency is 50 Hz? What is the
output frequency of a full-wave rectifier for the same input frequency?
9. What happens to the width of depletion layer of a p-n junction when it is
(i) forward biased,
(ii) reverse biased
10. Write any two distinguishing features between conductors, semiconductors and insulators on the
basis of energy band diagrams
11. Draw the circuit diagram of a half wave rectifier and explain its working
12. In the given diagram, is the junction diode forward biased or reverse biased?
13. What are the two types of semiconductors?
14. What are intrinsic semiconductors?
15. What are the methods to increase the conductivity of an intrinsic semiconductor?
16. What is doping?
17. Which are the two types of extrinsic semiconductors?
18. Which are the pentavalent impurities or donor impurities?
19. Give the values of barrier voltage for a Ge and Si diode.
20. Define knee voltage
21. Does diode obey Ohm’s law?
22. What you meant by the unidirectional property of a diode?
23. What you meant by rectification?
24. Why do a small current flow through the diode in the reverse biased condition?
25. What is the order of current in reverse bias?
