Electronic Devices and Circuits Questions & Answers - Page 10

46.

A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode is

A.

100

B.

99

C.

1.01

D.

0.99

Correct answer is A

β = (α / 1 - α) ⇒ (0.99 / 1 - 0.99) = 99 ⇒ Current gain = 1 + β = 100

47.

In which of these is reverse recovery time nearly zero?

A.

Zener diode

B.

Tunnel diode

C.

Schottky diode

D.

PIN diode

Correct answer is C

In schottky diode there is no charge storage and hence almost zero reverse recovery time.

48.

The most commonly used semiconductor material is

A.

silicon

B.

germanium

C.

mixture of silicon and germanium

D.

none of the above

Correct answer is A

Germanium is rarely used

49.

Work function is the maximum energy required by the fastest electron at 0 K to escape from the metal surface.

A.

True

B.

False

C.

Cannot say

D.

It depends

Correct answer is B

Work function is the minimum energy required by the fastest electron at 0 K to escape from the metal surface.

50.

At room temperature, the current in an intrinsic semiconductor is due to

A.

holes

B.

electrons

C.

ions

D.

holes and electrons

Correct answer is D

Intrinsic material has equal number of holes and electrons.