# Electronic Devices and Circuits MCQ Questions & Answers

Electronic Devices and Circuits MCQs : This section focuses on the "Electronic Devices and Circuits". These Multiple Choice Questions (MCQs) should be practiced to improve the Electronic Devices and Circuits skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

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

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Question 2

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

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Question 3

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

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Question 4

A potential of 7 V is applied to a silicon diode. A resistance of 1 K ohm is also in series with the diode. The current is

A. 7 mA
B. 6.3 mA
C. 0.7 mA
D. 0

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Question 5

A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately.

A. 30 pA
B. 40 pA
C. 50 pA
D. 60 pA

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Question 6

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

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Question 7

A transistor has two p-n junctions. The batteries should be connected such that

A. both junctions are forward biased
B. both junctions are reverse biased
C. one junction is forward biased and the other is reverse biased
D. none of the above

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Question 8

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

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Question 9

An amplifier without feedback has a voltage gain of 50, input resistance of 1 kΩ and output resistance of 2.5 kΩ. The input resistance of the current shunt -ve feedback amplifier using the above amplifier with a feedback factor of 0.2 is

A. 1/11 kΩ
B. 1/5 kΩ
C. 5 kW
D. 11 kW

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Question 10

An increase in temperature increases the width of depletion layer.

A. TRUE
B. FALSE

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Question 11

An LED has a rating of 2 V and 10 mA. It is used along with 6V battery. The range of series resistance is

A. 0 to 200 Ω
B. 200 - 400 Ω
C. 200 Ω and above
D. 400 Ω and above

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Question 12

As compared to an ordinary semiconductor diode, a Schottky diode

A. has lower cut in voltage
B. has higher cut in voltage
C. lower reverse saturation current
D. both (b) and (c)

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Question 13

As compared to an ordinary semiconductor diode, a Schottky diode

A. has higher reverse saturation current
B. has higher reverse saturation current and higher cut in voltage
C. has higher reverse saturation current and lower cut in voltage
D. has lower reverse saturation current and lower cut in voltage

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Question 14

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

A. holes
B. electrons
C. ions
D. holes and electrons

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Question 15

At very high temperatures the extrinsic semi conductors become intrinsic because

A. drive in diffusion of dopants and carriers
B. band to band transition dominants over impurity ionization
C. impurity ionization dominants over band to band transition
D. band to band transition is balanced by impurity ionization

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Question 16

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. 40.91, 0.58 μA
D. 41.10, 0.39 μA

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Question 17

Crossover distortion behaviour is characteristic of

A. class A O/P stage
B. class B O/P stage
C. class AB output stage
D. common pulse O/P state

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Question 18

Ferrite have

A. low copper loss
B. low eddy current loss
C. low resistivity
D. higher specific gravity compared to iron

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Question 19

If aac for transistor is 0.98 then βac is equal to

A. 51
B. 49
C. 47
D. 45

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Question 20

In a bipolar transistor the barrier potential

A. 0
B. a total of 0.7 V
C. 0.7 V across each depletion layer
D. 0.35 V

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Question 21

In a bipolar transistor which current is largest

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

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Question 22

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

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Question 23

In a p type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be

A. 0.5 eV above valence band
B. 0.28 eV above valence band
C. 0.1 eV above valence band
D. below the valence band

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Question 24

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

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Question 25

In an n channel JFET, the gate is

A. n type
B. p type
C. either n or p
D. partially n & partially p

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Question 26

In an n-p-n transistor biased for operation in forward active region

A. emitter is positive with respect to base
B. collector is positive with respect to base
C. base is positive with respect to emitter and collector is positive with respect to base
D. none of the above

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Question 27

In an n-p-n transistor, the majority carriers in the base are

A. electrons
B. holes
C. both holes and electrons
D. either holes or electrons

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Question 28

In p-n-p transistor the current IE has two components viz. IEP due to injection of holes from p-region to n-region and IE due to injection of electrons from n-region to p-region. Then

A. IEp and IEn are almost equal
B. IEp >> IEn
C. IEn >> IEp
D. either (a) or (c)

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Question 29

In which of these is reverse recovery time nearly zero?

A. Zener diode
B. Tunnel diode
C. Schottky diode
D. PIN diode

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Question 30

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

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Question 31

Recombination produces new electron-hole pairs

A. TRUE
B. FALSE

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Question 32

Secondary emission is always decremental.

A. TRUE
B. FALSE

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Question 33

The amount of photoelectric emission current depends on

A. frequency of incident radiation
B. intensity of incident radiation
C. both frequency and intensity of incident radiation
D. none of the above

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Question 34

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

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Question 35

The most commonly used semiconductor material is

A. silicon
B. germanium
C. mixture of silicon and germanium
D. none of the above

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Question 36

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

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Question 37

The number of doped regions in PIN diode is

A. 1
B. 2
C. 3
D. 1 or 2

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Question 38

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

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Question 39

The types of carriers in a semiconductor are

A. 1
B. 2
C. 3
D. 4

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Question 40

The word enhancement mode is associated with

A. tunnel diode
B. MOSFET
C. JFET
D. photo diode

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Question 41

When a voltage is applied to a semiconductor crystal then the free electrons will flow.

A. towards positive terminal
B. towards negative terminal
C. either towards positive terminal or negative terminal
D. towards positive terminal for 1 μs and towards negative terminal for next 1 μs

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Question 42

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

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Question 43

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

A. TRUE
B. FALSE

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Question 44

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

A. TRUE
B. FALSE

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