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ECE Objective Questions { Semiconductor Physics and Diodes }

29. In an unbiased P-N junction, thickness of depletion layer is of the order of
A. 0.005 gm
B. 0.5 gm
C. 5 gm
D. 10-1" m

30. A tunnel diode
A. has a small tunnel in its junction
B. is a point contact diode with a high reverse resistance
C. is a gallium arsenide device
D. is a highly-doped P-N junction device

31. When used in a power supply, the function of a Zener diode is to maintain a constant
A. output voltage
B. input voltage
C. output current irrespective of the load resistance
D. supply current

32. A step-recovery diode
A. has an extremely short recovery time
B. conducts equally well in both directions
C. is mainly used as a harmonic generator
D. is an ideal rectifier of high frequency signals.

33.  A semiconductor is
A. anothername for a transistor or a diode
B. characterized by a very large opposition to the flow of electrical current
C. a material whose conductivity is somewhere between that of a conductor and an insulator
D. a material used for making bipolar Transistor, Unij unction transistor, Field-effect transistors etc.

34.  Doping of semiconductors is
A. the process of purifying semiconductor materials
B. the process of adding certain impurities to the semiconductor material in controlled amounts
C. the process of converting semiconductor material into some from of active device like BJT, FET, UJT ect.
D. one of the steps used in fabrication of ICs

35. An N-type semiconducting material is formed by adding
A. some pentavalent impurity to the semiconductor material
B. some trivalent impurity to the semiconductor material
C. either of the two impurities mentioned above
D. none of these

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