Electronics and Communication Engineering questions and answers

Electronics and Communication Engineering Questions and Answers

Prepare for your Electronics and Communication Engineering exams/aptitude tests, assess your knowledge of electronics and communication equipment with these ECE questions and answers.

11.

Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C.

Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.

A.

Both A and R are true and R is correct explanation of A

B.

Both A and R are true but R is not a correct explanation of A

C.

A is true but R is false

D.

A is false but R is true

Correct answer is A

At 20°C, 4 nA, at 30°C, 8 nA, at 40°C, 16 nA, at 50°C, 32 nA.

13.

The types of carriers in a semiconductor are

A.

1

B.

2

C.

3

D.

4

Correct answer is B

Holes and electrons.

14.

In a degenerate n type semiconductor material, the Fermi level

A.

is in valence band

B.

is in conduction band

C.

is at the centre in between valence and conduction bands

D.

is very near valence band

Correct answer is B

This is due to high level of doping.

15.

Secondary emission is always decremental.

A.

True

B.

False

C.

Cannot say

D.

It depends

Correct answer is B

No explanation has been provided for this answer.

16.

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

A.

AB

B.

BC

C.

CD

D.

BD

Correct answer is B

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

17.

In a bipolar transistor, which current is largest

A.

collector current

B.

base current

C.

emitter current

D.

base current or emitter current

Correct answer is C

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

18.

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

Correct answer is B

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

19.

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

Correct answer is A

From Plank equation, E = hc/λ joule

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

20.

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

Correct answer is A

Zener diode is used only in voltage regulator circuits.