Electronic Devices and Circuits Questions & Answers

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1.

The minority carrier life time and diffusion constant in a semiconductor material are respectively 100 microsecond and 100 cm2/sec. The diffusion length is

A.

0.1 cm

B.

0.01 cm

C.

0.0141 cm

D.

1 cm

Correct answer is A

Diffusion length = √Dτ

2.

The normal operation of JFET is

A.

constant voltage region

B.

constant current region

C.

both constant voltage and constant current regions

D.

either constant voltage or constant current region

Correct answer is B

In major portion of drain characteristics, ID is constant.

3.

The power dissipation in a transistor is the product of

A.

emitter current and emitter to base voltage

B.

emitter current and collector to emitter voltage

C.

collector current and collector to emitter voltage

D.

none of the above

Correct answer is C

Maximum power dissipation occurs at collector junction.

4.

Which of the following is true as regards photo emission?

A.

Velocity of emitted electrons is dependent on light intensity

B.

Rate of photo emission is inversely proportional to light intensity

C.

Maximum velocity of electron increases with decreasing wave length

D.

Both holes and electrons are produced

Correct answer is C

As wavelength decreases, frequency increases and maximum velocity of electron increases.

5.

A p-n junction diode has

A.

low forward and high reverse resistance

B.

a non-linear v-i characteristics

C.

zero forward current till the forward voltage reaches cut in value

D.

all of the above

Correct answer is D

A p-n Junction has all these features.

6.

In which region of a CE bipolar transistor is collector current almost constant?

A.

Saturation region

B.

Active region

C.

Breakdown region

D.

Both saturation and active region

Correct answer is B

It is used as amplifier when it operates in this region.

7.

The word enhancement mode is associated with

A.

tunnel diode

B.

MOSFET

C.

JFET

D.

photo diode

Correct answer is B

MOSFET may be depletion mode or enhancement mode.

8.

Work function of oxide coated cathode is much lower than that of tungsten cathode.

A.

True

B.

False

C.

Cannot say

D.

None of the above

Correct answer is A

Therefore emission current from oxide coated cathode is more.

9.

A periodic voltage has following value for equal time intervals changing suddenly from one value to next... 0, 5, 10, 20, 50, 60, 50, 20, 10, 5, 0, -5, -10 etc. Then rms value of the waveform is

A.

31 V

B.

32 V

C.

insufficient data

D.

none of these

Correct answer is A

No explanation has been provided for this answer.

10.

Calculate the stability factor and change in IC from 25°C to 100°C for, β = 50, RB/ RE = 250, ΔIC0 = 19.9 nA for emitter bias configuration.

A.

42.53, 0.85 μA

B.

40.91, 0.58 μA

C.

40.58, 0.91 μA

D.

41.10, 0.39 μA

Correct answer is A

No explanation has been provided for this answer.


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