Bipolar Junction Transistors(BJT) MCQs - Electronics Device and Circuits

In this section of Electronic Devices and Circuits.It contain Transistors MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.

This Section covers below lists of topics :

Transistors Fundamentals MCQs.
Transistors ,npn,pnp MCQs.
Transistor common base connection (CB-configuration) MCQs.
Transistor Common emitter connection (CE-configuration) MCQs.
Transistor common collector connection (CC-configuration) MCQs.

Practice it now to sharpen your concept.

PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

1. A transistor has how many doped regions?

2. What is one important thing transistors do?

Amplify weak signals
Rectify line voltage
Regulate voltage
Emit light

3. Who invented the first junction transistor?

Bell
Faraday
Marconi
Schockley

4. In an npn transistor, the majority carriers in the base are

Free electrons
Holes
Neither
Both

5. The barrier potential across each silicon depletion layer is

0
0.3 V
0.7 V
1 V

6. The emitter diode is usually

Forward-biased
Reverse-biased
Nonconducting
Operating in the breakdown region

7. For normal operation of the transistor, the collector diode has to be

Forward-biased
Reverse-biased
Nonconducting
Operating in the breakdown region

8. The base of an npn transistor is thin and

Heavily doped
Lightly doped
Metallic
Doped by a pentavalent material

9. Most of the electrons in the base of an npn transistor flow

Out of the base lead
Into the collector
Into the emitter
Into the base supply

10. Most of the electrons in the base of an npn transistor do not recombine because they

Have a long lifetime
Have a negative charge
Must flow a long way through the base
Flow out of the base

11. Most of the electrons that flow through the base will

Flow into the collector
Flow out of the base lead
Recombine with base holes
Recombine with collector holes

12. The current gain of a transistor is the ratio of the

Collector current to emitter current
Collector current to base current
Base current to collector current
Emitter current to collector current

13. Increasing the collector supply voltage will increase

Base current
Collector current
Emitter current
None of the above

14. The fact that only a few holes are in the base region means the base is

Lightly doped
Heavily doped
Undoped
None of the above

15. In a normally biased npn transistor, the electrons in the emitter have enough energy to overcome the barrier potential of the

Base-emitter junction
Base-collector junction
Collector-base junction
Recombination path

16. When a free electron recombines with a hole in the base region, the free electron becomes

Another free electron
A valence electron
A conduction-band electron
A majority carrier

17. What is the most important fact about the collector current?

It is measured in milliamperes.
It equals the base current divided by the current gain.
It is small.
It approximately equals the emitter current.

18. If the current gain is 200 and the collector current is 100 mA, the base current is

0.5 mA
2 mA
2 A
20 A

19. The base-emitter voltage is usually

Less than the base supply voltage
Equal to the base supply voltage
More than the base supply voltage
Cannot answer

20. The collector-emitter voltage is usually

Less than the collector supply voltage
Equal to the collector supply voltage
More than the collector supply voltage
Cannot answer

21. The power dissipated by a transistor approximately equals the collector current times

Base-emitter voltage
Collector-emitter voltage
Base supply voltage
0.7 V

22. A small collector current with zero base current is caused by the leakage current of the

Emitter diode
Collector diode
Base diode
Transistor

23. A transistor acts like a diode and a

Voltage source
Current source
Resistance
Power supply

24. If the base current is 100 mA and the current gain is 30, the collector current is

300 mA
3 A
3.33 A
10 A

25. The base-emitter voltage of an ideal transistor is

0
0.3 V
0.7 V
1 V

26. If you recalculate the collector-emitter voltage with the second approximation, the answer will usually be

Smaller than the ideal value
The same as the ideal value
Larger than the ideal value
Inaccurate

27. In the active region, the collector current is not changed significantly by

Base supply voltage
Base current
Current gain
Collector resistance

28. The base-emitter voltage of the second approximation is

0
0.3 V
0.7 V
1 V

29. If the base resistor is open, what is the collector current?

0
1 mA
2 mA
10 mA

30. The current gain of a transistor is defined as the ratio of the collector current to the

Base current
Emitter current
Supply current
Collector current

31. The graph of current gain versus collector-current indicates that the current gain

Is constant
Varies slightly
Varies significantly
Equals the collector current divided by the base current

32. When the collector current increases, what does the current gain do?

Decreases
Stays the same
Increases
Any of the above

33. As the temperature increases, the current gain

Decreases
Remains the same
Increases
Can be any of the above

34. When the base resistor decreases, the collector voltage will probably

Decrease
Stay the same
Increase
Do all of the above

35. If the base resistor is very small, the transistor will operate in the

Cutoff region
Active region
Saturation region
Breakdown region

36. Ignoring the bulk resistance of the collector diode, the collector-emitter saturation voltage is

0
A few tenths of a volt
1 V
Supply voltage

37. Three different Q points are shown on a load line. The upper Q point represents the

Minimum current gain
Intermediate current gain
Maximum current gain
Cutoff point

38. If a transistor operates at the middle of the load line, an increase in the base resistance will move the Q point

Down
Up
Nowhere
Off the load line

39. If a transistor operates at the middle of the load line, an increase in the current gain will move the Q point

Down
Up
Nowhere
Off the load line

40. If the base supply voltage increases, the Q point moves

Down
Up
Nowhere
Off the load line

41. Suppose the base resistor is open. The Q point will be

In the middle of the load line
At the upper end of the load line
At the lower end of the load line
Off the load line

42. If the base supply voltage is disconnected, the collector emitter voltage will equal

0 V
6 V
10.5 V
Collector supply voltage

43. If the base resistor is shorted, the transistor will probably be

Saturated
In cutoff
Destroyed
None of the above

44. If the collector resistor decreases to zero in a base-biased circuit, the load line will become

Horizontal
Vertical
Useless
Flat

45. The collector current is 10 mA. If the current gain is 100, the base current is

1 microamp
10 microamp
100 microamp
1 mA

46. The base current is 50 microamp. If the current gain is 125, the collector current is closest in value to

40 microamp
500 microamp
1 mA
6 mA

47. When the Q point moves along the load line, the voltage increases when the collector current

Decreases
Stays the same
Increases
Does none of the above

48. When there is no base current in a transistor switch, the output voltage from the transistor is

Low
High
Unchanged
Unknown

49. A circuit with a fixed emitter current is called

Base bias
Emitter bias
Transistor bias
Two-supply bias

50. The first step in analyzing emitter-based circuits is to find the

Base current
Emitter voltage
Emitter current
Collector current

51. If the current gain is unknown in an emitter-biased circuit, you cannot calculate the

Emitter voltage
Emitter current
Collector current
Base current

52. If the emitter resistor is open, the collector voltage is

Low
High
Unchanged
Unknown

53. If the collector resistor is open, the collector voltage is

Low
High
Unchanged
Unknown

54. When the current gain increases from 50 to 300 in an emitter-biased circuit, the collector current

Remains almost the same
Decreases by a factor of 6
Increases by a factor of 6
Is zero

55. If the emitter resistance decreases, the collector voltage

Decreases
Stays the same
Increases
Breaks down the transistor

56. If the emitter resistance decreases, the

Q point moves up
Collector current decreases
Q point stays where it is
Current gain increases

57. BJT is:

Current-controlled device
Voltage-controlled device
Power-controlled device
None of the above

58. A BJT is in the saturation region if:

Base-emitter junction is reverse-biased and base-collector junction is forward-biased.
Both the junctions are reverse-biased.
Both the junctions are forward-biased.
Base-emitter junction is forward-biased and base-collector junction is reverse-biased.

59. Doping concentration of BJT is high in the:

Emitter region
Base region
Collector region
None of the above

60. If a transistor is operating with both of its junctions forward-biased, but with the collector-base forward-bias greater than emitter-base forward-bias, then it is operating in the:

Forward-active mode
Reverse-saturation mode
Reverse-active mode
Forward-saturation mode

61. In a bipolar transistor at room temperature, if the emitter current is doubled, the voltage across its base-emitter junction:

Doubles
Halves
Increases by 20 mV
No change occurs

62. The Early Effect in a bipolar transistor is caused by:

Base width modulation
Large collector-base reverse-bias
Large emitter-base forward-bias
Increase in junction temperature

63. β is the symbol of current gain for:

Common-base mode
Common-emitter mode
Common-collector mode
None of the above

64. α is the symbol of current gain for:

Common-base mode
Common-emitter mode
Common-collector mode
None of the above

65. Magnitude of α is:

< 1
> 1
< 0
None of the above

66. For the BJT, the impurity concentration in the emitter (E), base (B) and collector (C) are such that:

E > B > C
B > C > E
C = E = B
C > E > B

67. When a junction transistor is operated under saturated conditions:

Both the CB and EB junction are forward-biased
The CB junction is forward-biased but the EB junction is reverse-biased
The CB junction is reverse-biased but the EB junction is forward-biased
None of the above

68. The modulation of effective base width by collector voltage is known as Early Effect; hence reverse collector voltage:

Increases both α and β
Decreases both α and β
Increases α but decreases β
Decreases β but increases α

69. In a transistor as an amplifier, the reverse saturation current:

Doubles for every C rise in temperature
Doubles for every 10º C rise in temperature
Decreases linearly with temperature
Increase linearly with temperature

70. Which configuration of bipolar transistors of similar geometry has the highest current gain, bandwidth product for:

n–p–n Ge transistor
p–n–p Si transistor
p–n–p Ge transistor
n–p–n Si transistor

71. Base-to-emitter voltage is forward-biased transistor decreases with the increase of temperature at the following rate:

2.5 mv/°C
25 mv/°C
0.25 mv/°C
0.6 mv/°C

72. In an nPn transistor with normal bias

Only holes cross the collector junction
Only the majority carries cross the collection junction
The emitter junction has a high resistance
The emitter junction is forward biased and collector junction is reverse biased

73. In a transistor, which normal biasing, the

Emitter junction is high and collector junction has low resistance
Emitter junction has low and collector junction has high resistance
Both emitter and collector junction have low resistance
Both emitter and collector junction have high resistance

74. the most commonly used transistor circuit arrangement is

Common base
Common emitter
Common collector
None of these

75. Emitter of transistor is doped

Heavily
Lightly
Moderately
None of these

76. for transistor action

The base region must be very thin and lightly doped
The emitter junction should be forward biased and collector junction should be reverse biased emitter should be heavily doped so that it can
Supply the required amount of majority carriers
All of these

77. I_CBO is the current that flows when some DC voltage is applied

In the forward direction to the emitter junction with collector open
In the reverse direction to the emitter Junction with collector open
In the reverse direction to the collector Junction with emitter open
Is the forward direction to the collector Junction with emitter open

78. The magnitude of current I_CBO

Depends largely upon the emitter doping
Depends largely upon the emitter base junction bias potential
Increase with increase in temperature
Is generally greater in Silicon than in Germanium transistor

79. The current I_CBO flows in the

Emitter and base leads
Collector and base leads
Emitter and collector leads
None of these

80. The arrowhead on the transistor symbol points In the direction of

Electrons flow in the emitter region
Minority Carriers flow in the emitter region
Majority carriers flow in the emitter region
Conventional current flow in the emitter region

81. The Silicon transistor are more widely used then Germanium transistor because

They have smaller leakage current
They have better ability to dissipate heat
They have smaller depletion layers
They have larger the current carrying capacity

82. The CE amplifier circuit are preferred over CB amplifier circuits because they have

low amplification factor
Larger amplification factor
High Input resistance and low output resistance
None of these

83. A transistor, when connected in CE mode, has

Low input resistance and low output resistance
High input resistance and high output resistance
High input resistance and low output resistance
A medium input resistance and high output resistance

84. In CE mode of transistor, the most noticeable effect of a small increase in temperature is

The increase in output resistance
The increase in leakage current ICEO
The decrease in AC current gain
Increase in AC current gain

85. The current I_CEO is

The emitter current in the CC connected transistor with zero base current
The collector current in CE connected transistor with zero emitter current
The collector current in the CE connected transistor with zero base current
Same as ICBO

86. In CE configuration, output v-i characteristics are drawn by taking

VCE versus IC for constant value of IE
VCE versus IC for constant value of IB
VCE versus IE for constant value of VCB
none of these

87. In CE configuration, the input VI characteristics are drawn by taking

VCE versus IC for constant value of IE
VBE versus IC for constant value of IB
VBE versus IB for constant value of IC
VB versus IB for constant value of VCE

88. A transistor is said to be in quiescent state when

It is unbiased
No current flows through it
Emitter junction is just biased equal to Collector Junction
No signal is applied to the input

89. The emitter current in a Junction with normal bias

Is almost equal to base current
Is equal to the sum of IB and IC
Changes greatly by small change in collector bias voltage
Is equal to ICBO

90. The beta of transistor maybe determined directly from the curve plotted between

VCE and IC for constant IB
VCE and IC for constant IE
VCE and IE for constant IB
VBE and IE for constant VCE

91. In CB configuration, the output VI characteristics of a transistor are drawn by taking

VCB versus IC for constant IE
VCB versus IB for constant IE
VCE versus IC for constant IE
VCE versus IB for constant IE

Electronics Device and Circuits – Bipolar Junction Transistors(BJT) MCQs