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Elecs- Indiabix (Terms) > Electrnic Devices 2- BJT > Flashcards

Electrnic Devices 2- BJT Flashcards

1
Q

What is the ratio of IC to IB?

A

either betaDC or hFE, but bit alphaDC

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2
Q

For normal operation of a pnp BJT, the base must be ________ with respect to the emitter and ________ with respect to the collector.

A

negative, positive

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3
Q

When a transistor is used as a switch, it is stable in which two distinct regions?

A

saturation and cutoff

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4
Q

For a silicon transistor, when a base-emitter junction is forward-biased, it has a nominal voltage drop of

A

0.7 V.

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5
Q

What does betaDC vary with?

A

both IC and ºC

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6
Q

What are the two types of bipolar junction transistors?

A

npn and pnp

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7
Q

The value of betaDC

A
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8
Q

A transistor data sheet usually identifies betaDC as

A

hFE

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9
Q

What is the ratio of IC to IE?

A

either betaDC / (betaDC + 1) or alphaDC, but not DC

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10
Q

Which of the following is true for an npn or pnp transistor?

A

IE = IB + IC

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11
Q

What is the order of doping, from heavily to lightly doped, for each region?

A

emitter, collector, base

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12
Q

In what range of voltages is the transistor in the linear region of its operation?

A

0.7 < VCE < VCE(max)

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13
Q

The magnitude of dark current in a phototransistor usually falls in what range?

A

nA

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14
Q

What is (are) general-purpose/small-signal transistors case type(s)?

A

TO-18
TO-92
TO-39
TO-52
all of the above

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15
Q

What is (are) common fault(s) in a BJT-based circuit?

A

opens or shorts internal to the transistor
open bias resistor(s)
external opens and shorts on the circuit board
all of the above

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16
Q

The dc load line on a family of collector characteristic curves of a transistor shows the

A

saturation region.
cutoff region.
active region.
all of the above

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17
Q

Clipping is the result of

A

the input signal being too large.
the transistor being driven into saturation.
the transistor being driven into cutoff.
all of the above

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18
Q

Which transistor bias circuit arrangement provides good stability using negative feedback from collector to base?

A

collector-feedback bias

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19
Q

What is the dc input resistance at the base of a BJT?

A

betaDCRE

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20
Q

Which transistor bias circuit provides good Q-point stability with a single-polarity supply voltage?

A

voltage-divider bias

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21
Q

Ideally, for linear operation, a transistor should be biased so that the Q-point is

A

halfway between cutoff and saturation.

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22
Q

The most stable biasing technique used is the

A

voltage-divider bias.

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23
Q

Emitter bias requires

A

both positive and negative supply voltages.

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24
Q

Which transistor bias circuit arrangement has poor stability because its Q-point varies widely with DC?

A

base bias

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25
Q

What is the most common bias circuit?

A

voltage-divider

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26
Q

At saturation the value of VCE is nearly ________, and IC = ________.

A

zero, I(sat)

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27
Q

Voltage-divider bias has a relatively stable Q-point, as does

A

collector-feedback bias.

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28
Q

The linear (active) operating region of a transistor lies along the load line below ________ and above ________.

A

saturation, cutoff

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29
Q

The input resistance of the base of a voltage-divider biased transistor can be neglected

A

only if the base current is much smaller than the current through R2 (the lower bias resistor).

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30
Q

Which transistor bias circuit arrangement provides good Q-point stability, but requires both positive and negative supply voltages?

A

emitter bias

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31
Q

Changes in betaDC result in changes in

A

IC.
VCE.
the Q-point.
all of the above

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32
Q

How much is the base-to-emitter voltage of a transistor in the “on” state?

A

0.7 V

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33
Q

How many layers of material does a transistor have?

A

3

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34
Q

Which of the following equipment can check the condition of a transistor?

A

Current tracer
Digital display meter (DDM)
Ohmmeter (VOM)
All of the above

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35
Q

For what kind of amplifications can the active region of the common-emitter configuration be used?

A

Voltage
Current
Power
All of the above

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36
Q

In the active region, while the collector-base junction is ________-biased, the base-emitter is ________-biased.

A

reverse, forward

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37
Q

A transistor can be checked using a(n) ________.

A

curve tracer
digital meter
ohmmeter
Any of the above

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38
Q

What range of resistor values would you get when checking a transistor for forward- and reverse-biased conditions by an ohmmeter?

A

100 to a few k, exceeding 100 k

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39
Q

What is (are) the component(s) of electrical characteristics on the specification sheets?

A

On
Off
Small-signal characteristics
All of the above

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40
Q

In which region are both the collector-base and base-emitter junctions forward-biased?

A

Saturation

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41
Q

Which of the following is (are) the terminal(s) of a transistor?

A

Emitter
Base
Collector
All of the above

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42
Q

Which of the following configurations can a transistor set up?

A

Common-base
Common-emitter
Common-collector
All of the above

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43
Q

What does a reading of a large or small resistance in forward- and reverse-biased conditions indicate when checking a transistor using an ohmmeter?

A

Faulty device

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44
Q

Determine the value of alpha when beta= 100.

A

Alpha = Beta/(1+Beta).
Alpha = 100.
Alpha = 100/1+100.
Alpha = 100/101.
Alpha = 0.99.

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45
Q

Transistors are ________-terminal devices.

A

3

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46
Q

Which of the following can be obtained from the last scale factor of a curve tracer?

A

BetaAC

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47
Q

betaDC

A

IC / IB

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48
Q

How many carriers participate in the injection process of a unipolar device?

A

1

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49
Q

What are the ranges of the ac input and output resistance for a common-base configuration?

A

10 –100 , 50 k –1 M

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50
Q

What is the most frequently encountered transistor configuration?

A

Common-emitter

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51
Q

Which of the following regions is (are) part of the output characteristics of a transistor?

A

Active
Cutoff
Saturation
All of the above

52
Q

How many individual pnp silicon transistors can be housed in a 14-pin plastic dual-in-line package?

A

4

53
Q

In what decade was the first transistor created?

A

1940s

54
Q

Most specification sheets are broken down into

A

maximum ratings
thermal characteristics
electrical characteristics
All of the above

55
Q

What is (are) the component(s) of most specification sheets provided by the manufacturer?

A

Maximum ratings
Thermal characteristics
Electrical characteristics
All of the above

56
Q

What is the ratio of the total width to that of the center layer for a transistor?

A

150:1

57
Q

Which component of the collector current IC is called the leakage current?

A

Minority

58
Q

For the BJT to operate in the active (linear) region, the base-emitter junction must be ________-biased and the base-collector junction must be ________-biased.

A

forward, reverse

59
Q

The cutoff region is defined by IB ________ 0 A.

A

S(beta)

60
Q

Which of the following is (are) related to an emitter-follower configuration?

A

The input and output signals are in phase.
The voltage gain is slightly less than 1.
Output is drawn from the emitter terminal.
All of the above

61
Q

At what region of operation is the base-emitter junction forward biased and the base-collector junction reverse biased?

A

Linear or active

62
Q

In a voltage-divider circuit, which one of the stability factors has the least effect on the device at very high temperature?

A

S(beta)

63
Q

Which of the following is (are) a stability factor?

A

S(ICO)
S(VBE)
S(beta)
All of the above

64
Q

Which of the following currents is nearly equal to each other?

A

IE and IC

65
Q

Which of the following voltages must have a negative level (value) in any npn bias circuit?

A

VBC

66
Q

For the typical transistor amplifier in the active region, VCE is usually about ________ % to ________ % of VCC.

A

25, 75

67
Q

For the BJT to operate in the saturation region, the base-emitter junction must be ________-biased and the base-collector junction must be ________-biased

A

forward, forward

68
Q

The ratio of which two currents is represented by beta?

A

IC and IB

69
Q

Which of the following is assumed in the approximate analysis of a voltage divider circuit?

A

IB is essentially zero amperes.
R1 and R2 are considered to be series elements.
betaRE >_10R2
All of the above

70
Q

The saturation region is defined by VCE ________ VCEsat.

A

<_

71
Q

Which of the following is (are) the application(s) of a transistor?

A

Amplification of signal
Switching and control
Computer logic circuitry
All of the above

72
Q

The current gain for the Darlington connection i

A

beta1(beta2)

73
Q

Which of the following configurations has the lowest output impedance?

A

Emitter-follower

74
Q

Which of the h-parameters corresponds to re in a common-base configuration?

A

hib

75
Q

Which of the following is referred to as the reverse transfer voltage ratio?

A

hr

76
Q

Which of the following conditions must be met to allow the use of the approximate approach in a voltage-divider bias configuration?

A

beta re<10R2

77
Q

For a common-emitter amplifier, the purpose of swamping is

A

to reduce the effects of r’e

78
Q

What is the typical value of the current gain of a common-base configuration?

A

Less than 1

79
Q

What is the most important r parameter for amplifier analysis?

A

re′

80
Q

An emitter-follower is also known as a

A

common-collector amplifier.

81
Q

The ________ model fails to account for the output impedance level of the device and the feedback effect from output to input.

A

re

82
Q

You have a need to apply an amplifier with a very high power gain. Which of the following would you choose?

A

common-emitter

83
Q

What is the voltage gain of a feedback pair connection?

A

1

84
Q

A common-emitter amplifier has ________ voltage gain, ________ current gain, ________ power gain, and ________ input impedance.

A

high, high, high, low

85
Q

What is the range of the input impedance of a common-base configuration?

A

A few ohms to a maximum of 50

86
Q

The advantage that a Sziklai pair has over a Darlington pair is

A

less input voltage is needed to turn it on.

87
Q

What is the typical range of the output impedance of a common-emitter configuration?

A

40 k to 50 k

88
Q

What is the unit of the parameter ho?

A

Siemen

89
Q

What is the range of the current gain for BJT transistor amplifiers?

A

less than 1
1 to 100
above 100
All of the above

90
Q

For the common-emitter fixed-bias configuration, there is a ________ phase shift between the input and output signals.

A

180

91
Q

What does the negative sign in the voltage gain of the common-emitter fixed-bias configuration indicate?

A

The output and input voltages are 180º out of phase.

92
Q

Which one of the following configurations has the lowest input impedance

A

Common-base

93
Q

Which of the following represent(s) the advantage(s) of the system approach over the r-model approach?

A

Thevenin’s theorem can be used.
The effect of changing the load can be determined by a simple equation.
There is no need to go back to the ac equivalent model and analyze the entire network.
All of the above

94
Q

The differential amplifier has

A

two inputs and one output.

95
Q

The emitter-follower configuration has a ________ impedance at the input and a ________ impedance at the output.

A

high, low

96
Q

The differential amplifier produces outputs that are

A

the difference of the two input voltages.

97
Q

The ________ model suffers from being limited to a particular set of operating conditions if it is to be considered accurate.

A

hybrid equivalent

98
Q

Under which of the following condition(s) is the current gain Av=beta?

A

ro >_10RC and RB >_10re

99
Q

The ________ configuration is frequently used for impedance matching.

A

emitter-follower

100
Q

When the bypass capacitor is removed from a common-emitter amplifier, the voltage gain

A

decreases.

101
Q

In a common-base amplifier, the input signal is connected to the

A

emitter.

102
Q

Which of the following is (are) true to achieve a good overall voltage gain for the circuit?

A

The effect of Rs and RL must be considered as a product and evaluated individually.

103
Q

To analyze the common-emitter amplifier, what must be done to determine the dc equivalent circuit?

A

replace coupling and bypass capacitors with opens

104
Q

For the common-emitter amplifier ac equivalent circuit, all capacitors are

A

effectively shorts.

105
Q

Under which of the following conditions is the output impedance of the network approximately equal to RC for a common-emitter fixed-bias configuration?

A

ro >_10RC

106
Q

Which of the following gains is less than 1 for a common-base configuration?

A

Ai

107
Q

Which of the following define(s) the conversion efficiency?

A

Ac power to the load/dc power supplied

108
Q
A

Which of the following should be done to obtain the ac equivalent of a network?

109
Q

In an unbypassed emitter bias configuration hie replaces ________ in the re model.

A

beta re

110
Q

Which of the following is (are) true regarding the input impedance for frequencies in the midrange<_100 kHz of a BJT transistor amplifier?

A

The input impedance is purely resistive.
It varies from a few ohms to megohms.
An ohmmeter cannot be used to measure the small-signal ac input impedance.
All of the above

111
Q

For the collector dc feedback configuration, there is a ________ phase shift between the input and output signals.

A

180

112
Q

A common-collector amplifier has ________ input resistance, ________ current gain, and ________ voltage gain.

A

high, high, low

113
Q

The total gain of a multistage amplifier is the __

A

sum of dB voltage gains

114
Q

Which of the following configurations has an output impedance Zo equal to RC?

A

Fixed-bias common-emitter
Common-emitter voltage-divider with bypass capacitor
Common-emitter voltage-divider without bypass capacitor
All of the above

115
Q

For a common-emitter amplifier, the purpose of the emitter bypass capacitor is

A

to maximize amplifier gain.

116
Q

For BJT amplifiers, the ________ gain typically ranges from a level just less than 1 to a level that may exceed 1000.

A

current

117
Q

Which of the following configurations has a voltage gain of –RC /re?

A

Fixed-bias common-emitter and voltage-divider with bypass capacitor

118
Q

Which of the following is (are) true regarding the output impedance for frequencies in the midrange<_100 kHz of a BJT transistor amplifier?

A

The output impedance is purely resistive.
It varies from a few ohms to more than 2 M.
An ohmmeter cannot be used to measure the small-signal ac output impedance.
All of the above

119
Q

What is the limit of the efficiency defined by = Po / Pi?

A

Less than 1

120
Q

What is re equal to in terms of h parameters?

A

hre / hoe

121
Q

What is the controlling current in a common-base configuration?

A

Ie

122
Q

Which of the following techniques can be used in the sinusoidal ac analysis of transistor networks?

A

Small- or large-signal

123
Q

The input impedance of a BJT amplifier is purely ________ in nature and can vary from a few ________ to ________.

A

resistive, ohms, megohms

124
Q

The ________ the source resistance and/or ________ the load resistance, the less the overall gain of an amplifier.

A

larger, smaller

125
Q

A Darlington pair provides beta ________ for ________ input resistance.

A

multiplication, increased

126
Q

A Darlington pair amplifier has

A

a low voltage gain and a high input impedance

Elecs- Indiabix (Terms) (6 decks)

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