Electronics and Communication Engineering - Electronic Devices and Circuits

31. 

A zener diode is used in

A. voltage regulator circuit
B. amplifier circuits
C. both voltage regulator and amplifier circuit
D. none of the above

Answer: Option A

Explanation:

Zener diode is used only in voltage regulator circuits.


32. 

A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. h = 6.6 x 10-34 J sec.

A. 2.26 eV
B. 1.98 eV
C. 1.17 eV
D. 0.74 eV

Answer: Option A

Explanation:

From Plank equation joule

to convert it into electron volt it will be divided by 1.6 x 10-19.


33. 

In a zener diode

A. the forward current is very high
B. sharp breakdown occurs at a certain reverse voltage
C. the ratio v-i can be negative
D. there are two p-n junctions

Answer: Option B

Explanation:

When reverse voltage equals breakdown value it starts conducting and voltage does not increase further.


34. 

In a bipolar transistor which current is largest

A. collector current
B. base current
C. emitter current
D. base current or emitter current

Answer: Option C

Explanation:

Emitter current is larger, collector current is slightly less than emitter current and base current is very small.


35. 

The v-i characteristics of a FET is shown in figure. In which region is the device biased for small signal amplification

A. AB
B. BC
C. CD
D. BD

Answer: Option B

Explanation:

Small signal amplifier operation is in constant current region of characteristics.