ITEC 320 Exam 3 Flashcards Preview

Module 4, Lesson 3 > ITEC 320 Exam 3 > Flashcards

Flashcards in ITEC 320 Exam 3 Deck (139):
1

Field-effect transistor

A transistor controlled by voltage rather than by current. The flow of current is controlled by the effects of an electric field.

2

Gate

An element in a FET. It is the control element of the devices. It corresponds to the base of a bipolar transistor.

3

Drain

The terminal of a FET that is the drain for charge carriers from the FET channel.

4

Source

In general, the origin of the electrical energy supplied to a device. In FET's, it is one of the electrodes.

5

The FET is a semiconductor device in which output current is controlled by

An electric field or gate

6

The control element in a FET is the

Gate

7

The point at which an increase in voltage from source to drain no longer produces an increase in current is called

Saturation current

8

When the negative gate voltage (VGS) stops the current flow from source to drain, the FET has reached its

Cutoff voltage

9

Does the FET have a high or low input impedance

High

10

Common-source amplifier

An amplifier in which an FET is the active device. The source of the FET is common to the input and output circuits. Input is applied to the gate and the output is applied to the drain

11

Does the common-source FET amplifier require complicated bias arrangements, why or why not

No, because we do not need reverse bias and its self-biased.

12

Common-source FET amplifiers have a high input

Impedance

13

How many degrees is the phase shift between input and output signals in a common-source amplifier

180 degrees

14

What type of input signal does a common-source FET amplifier require to produce a large output signal

Powerful input signal (4/10v)

15

Source-follower

An amplifier where the drain is common to the input and output circuits. Input is applied to the gate. Output occurs at the source. Voltage gain is less than 1

16

Emitter-follower

A transistor stage in which the collector is common to the input and output circuits. Input is applied to the base. Output occurs at the emitter. Voltage gain is less than 1

17

In a source-follower circuit, how many degrees is the output inverted from the input

Its not, they follow one another or zero

18

Does a source-follower have a high or low output impedance

Low

19

The voltage gain of a source-follower is less than

1

20

The source-follower has a fairly poor what

Gain

21

Does the source-follower circuit have a high or low input impedance

High

22

The FET is a semiconductor device in which an electrical field within the device controls

Output current

23

You can increase or decrease the electric field within a FET with the amount of voltage applied to the

Gate

24

The electric field in a FET determines the amount of current flowing from the

Source to drain

25

An advantage of a FET is its

High input impedance

26

FET's use what as part of their circuitry

Self-bias

27

FET's need what to produce a large output at the load

A small amount of input power

28

A common-source amplifier accepts and amplifies a

Fairly wide range of frequencies

29

Voltage gain formula

Output voltage/input voltage

30

The output of a source-follower is take from a resistor in the

Source circuit

31

A source-follower is used in many

Impedance matching situations

32

MOSFET

Metal oxide semiconductor field-effect transistor. A FET with an insulated gate (IGFET.) The metal gate is insulated from the semiconductor by an oxide layer.

33

2 types of MOSFETs

Enhancement-types (turned off) or depletion-types (turned on)

34

Types MOSFETs can be divided into

N-types and P-types

35

IGFET

Insulated gate FET

36

Depletion mode

MOSFET operation in which changing the gate-to-source voltage from zero to some other value decreases the drain current. Turned on, but can be turned off when a control voltage is applied to the gate terminal

37

Enhancement mode

MOSFET operation in which changing the gate-to-source voltage from zero to some other value increases the drain current. Enhancement is turned off, but can be turned on when a control voltage is applied to the gate terminal

38

Majority carrier

The major carrier in semiconductor materials. Electrons in N-types. Holes in P-types.

39

Substrate

The surface, or under layer, on which electronic circuits are fabricated. It can be insulating materials, printed circuits, or photocells.

40

Dual-gate MOSFET

Also called a tetrode MOSFET. A MOSFET having two independent gates. Circuit action is controlled by either gate. Provides flexibility

41

Is there a PN junction between the gate and source in a MOSFET

No

42

A MOSFET has a (higher, lower) input resistance than a JFET

Higher

43

Is a depletion-mode MOSFET a normally off device

No

44

The enhancement-mode MOSFET has a (diffused, induced) conducting channel

Induced

45

In an enhancement-mode MOSFET with 0V bias, an AC signal operates the device on the

Positive AC alternations

46

VHF

The very high frequency range. It extends from 30 to 300 megahertz

47

UHF

The ultra high frequency range. It extends from 300 to 3000 megahertz

48

What are three basic circuit arrangements for a MOSFET

Common-source, common-gate, and common-drain

49

In what configuration is the source-follower circuit connected

Common-gate

50

The common-gate amplifier has a (higher, lower) voltage gain than the common-source amplifier

Lower

51

The common-gate circuit matches what to what impedance

Low source resistance impedance to a high source resistance impedance

52

The common what circuit inverts the signal 180 degrees

Source

53

Mixers

A circuit that accepts two or more input signals and combines them in some specific manner

54

Modulator

A circuit that varies the amplitude or frequency of sine-wave voltage according to variations of another voltage or current.

55

Automatic gain control (AGC)

A circuit or system that maintains the output signal level of an electronic device constant, compensating fro changes of input signal level.

56

Automatic volume control (AVC)

A circuit or system that maintains the output volume of a sound-producing system constant, compensating for changes of input signal level

57

Why are MOSFETs useful in communications circuits

High input resistance and low input capacitance

58

You can operate the gates in a dual-gate MOSFET

Independently

59

A gain control voltage appearing at one of the gates acts as an added

Additional bias voltage

60

For an N-channel MOSFET, a more (negative, positive) voltage is needed to reduce the gain of the device

Negative

61

The gate of a MOSFET is

Insulated from the channel by an oxide layer

62

An insulated gate of a MOSFET provides

An even higher input resistance than the JFET

63

A MOSFET can operate with either what appearing at its gate

Polarity

64

In an N-channel MOSFET, a (negative, positive gate voltage) increases drain current

Positive gate voltage

65

In an N-channel depletion-mode MOSFET, the drain-to-source voltage is always applied with

The drain more positive than the source

66

The depletion-mode MOSFET conducts a substantial amount of current

With a gate voltage of zero

67

The enhancement-mode MOSFET conducts almost no drain current

When the gate is zero

68

In the common-gate circuit, the gate is common to

Both the input and the output

69

The common-gate circuit is a

Voltage amplifier

70

The two gates of a dual-gate MOSFET can be operated

Independently

71

Photoelectric effect

The effect produced by some materials when they are subjected to light.

72

Light sensitive

When a device is sensitive to various amounts of light and converts the changes of light intensity into changes of some electrical characteristic

73

Photoconductive cell

A type of photocell which acts as a variable resistor

74

Photovoltaic cell

A type of photocell which builds up a charge depending on the amount of light hitting it

75

Photocells

Also called photoelectric cell (PEC). A light-sensitive cell that converts variations of light intensity into variations of some electrical characteristic

76

Photoresistive cells

A photoelectric cell where the electrical resistance varies inversely with the intensity of light which strikes it

77

Bulk photoconductor

A term used to describe large photoconductive cells because of their bulk construction

78

Wavelength

The distance between two corresponding points of two consecutive waves.

79

What is a photoelectric device

A device used to detect distance, absence, or presence of an object by using a light transmitter.

80

What is a photoconductive cell

A light variable resistor

81

Can a photoconductive cell be improperly biased

No

82

Does the resistance of a photoconductive cell increase or decrease with an increase in light

Decrease

83

In a photocell, is the increase in resistance exactly proportional to the decrease in light

No

84

Thyristor

A term used to describe a group of 4-layer semiconductor devices that can be pulsed into conduction, but can be turned off only by interrupting the applied voltage. SCRs and traics are thyristors

85

Silicon controlled rectifier (SCR)

A solid-state switching device that does not require any control current after it has been turned on. An SCR acts as an open circuit until a positive potential is applied to its gate terminal. The other two electrodes are the anode and cathode.

86

Forward breakover voltage

The value of forward bias voltage applied to the gate of a thyristor that causes it to become highly conductive

87

What is the control electrode in the SCR

Gate

88

The SCR does not turn on until the forward bias from the anode to cathode reaches a certain value. What is the value

Forward breakover voltage

89

In an AC circuit, what does an increase in an SCR's gate current cause

Forward breakover voltage may decrease

90

Does the gate of an SCR lose control once the SCR is turned on

No

91

During the negative half cycle of the waveform, the SCR is

Reverse biased

92

What must you increase to lower breakover voltage

Gate current

93

Will the amount of power received increase or decrease if the gate triggering pulses are delayed more

Decrease

94

Can you trigger a thyristor with a manually-operated circuit

Yes

95

Do you use SCRs to control electrical power

Yes

96

List three uses of SCRs

Relays, lamps, and dimmers

97

What is the main advantage of an SCR

Small current triggering a larger current or voltage

98

Two thyristors are the

Triac and diac

99

SCRs use

3 electrodes

100

The gate of an SCR

Is the control point

101

An SCR is off when it is

Reverse biased

102

An SCR does not turn on until the forward bias reaches

The forward breakover voltage

103

Once an SCR is turned on

THe gate loses control of the cathode-to-anode current

104

In a manually-operated SCR, the SCR and load are

In series with an AC supply voltage

105

In a manually-operated SCR, you can ignore the negative half of the cycle since it will

Reverse bias the thyristor during that half cycle

106

The main use of an SCR is to

Control electrical power and convert electrical power

107

SCRs are used in alarm circuits because they can be triggered with

Very small currents

108

A component that allows signal to remain electrically independent of the following circuit is called a

Isolater

109

Between what circuits is an isolator useful in coupling a signal

Control circuits and power circuits

110

A circuit that uses an isolator converts what energy to what energy

electrical energy to light energy

111

The signal output from a photoconductor used as an isolator is an amplified replica of the input. T or F

True

112

The signal output from a photoconductor used as an isolator is 180 degrees out of phase with the input. T or F

False

113

The resistance of a photoconductive cell decreases with

An increase in light intensity

114

The light-sensitive material in a photoconductive cell is formed in a thin layer on a

glass and ceramic substrate

115

Large photoconductive cells are able to withstand

Relatively high operating voltages (300 VDC)

116

In a schematic of a photoconductive cell, an arrow pointing toward the device indicates

The device is light sensitive

117

In an intrusion detector circuit, when an intruder interrupts the light beam

The resistance of the photocell suddenly increases

118

In an intrusion detector circuit

A photocell is placed in series with a relay coil and a power

119

In an intrusion detector circuit, focusing a narrow beam of light from a distant light source on the light-sensitive element of the photocell

Keeps the resistance of the series circuit low

120

An isolator is a device that

Couples a signal voltage between two isolated circuits

121

In a basic isolator circuit, a signal voltage causes the lamp to

Vary in intensity

122

In a basic isolator circuit, light from the lamp causes the resistance of the photoconductor to

Vary

123

Voltage regulator circuits are used to

Filter circuits and refine the filtering process

124

Voltage regulator circuits provide voltage regulation for

Power supplies

125

In a power source, each component adds up to

An internal resistance in series with the output current

126

A what is an effective shunt regulator

Zener diode

127

Voltage output changes can occur because of a variation in

Line voltage input

128

The smaller the percentage of regulation

The better the regulator

129

In a shunt voltage regulator, the regulator acts as an

Zener diode in parallel with the load

130

In a series voltage regulator, the regulator acts as an

Transistor in series with the load

131

One use of a series voltage regulator is as a

Ripple filter

132

An increase in current will cause the series voltage regulator to

Decrease in resistance

133

An amplifier is a circuit that increases the amplitude of a

Alternating waveform

134

To determine how much an amplifier can increase a signal, you determine

Gain

135

Amplifiers may amplify either

Current or voltage

136

When you need large gains, you can connect

Cascaded amplifiers

137

The total gain of two amplifiers connected in cascade is

The product of their individual gains

138

An enhancement mode MOSFET acts as a push button switch

Turned off

139

An depletion mode MOSFET acts as a push button switch

Turned on