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ELECS > MODULE 2: Semicon and diode equivalent circuits > Flashcards

MODULE 2: Semicon and diode equivalent circuits Flashcards

1
Q

They can be made to act as a conductor at one time
and as an insulator at another depending upon the
manipulation done with its inherent nature.

A

semiconductors

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2
Q

Semiconductor materials are insulators at absolute
____temperature and conduct electricity in a
limited way at room temperature.

A

zero

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3
Q

semiconductors have exactly _____ valence

electrons.

A

four

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4
Q

The defining property of a semiconductor material
is that it can be _____with impurities that alter its
electronic properties in a controllable way.

A

doped

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5
Q

The most common semiconductor materials are

_____.

A

Silicon (Si) and Germanium (Ge)

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6
Q

Compound semiconductors like _______are also in common use.

A

Gallium Arsenide
(GaAs), Aluminum Arsenide (AlAs) and Gallium
Phosphide (GaP)

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7
Q

It is a non-metallic element which was discovered in

1823 and found extensively in the earth’s crust.

A

SILICON

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8
Q

It is a brittle, grayish-white earth element which was

discovered in 1886.

A

GERMANIUM

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9
Q

Atoms in a semiconductor are arranged in

the form of a _______

A

crystal lattice.

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10
Q

Each atom shares its 4 valence electrons with
4 neighboring atoms.This electron-pair bond is commonly referred
to as a _____ bond.

A

covalent

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11
Q

It refers to pure materials and therefore free from
impurities that exist naturally like pure silicon and
pure germanium.

A

Intrinsic Semiconductor

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12
Q

It has equal numbers of negative carriers (electrons)

and positive carriers (holes).

A

Intrinsic Semiconductor

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13
Q

If a voltage is applied, then both the electron and the

hole can contribute to a small current flow.

A

Intrinsic Semiconductor

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14
Q

It refers to semiconductor materials doped with
some impurities so as to alter their original
electrical properties, normally to______their
electrical conductivities.
Electronics

A

Extrinsic Semiconductor

INCREASE

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15
Q

It is the process of adding pentavalent or trivalent
impurities to an intrinsic material in
order to increase the

A

DOPING

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16
Q

ANOTHER TERM FOR pentavalent or trivalent

impurities

A

DOPANTS

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17
Q

means that only few impurities are added

resulting to a higher resistance (lower conductivity)

A

LIGHTLY DOPED

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18
Q

means that more impurities are added

resulting to a lower resistance (higher conductivity)

A

HEAVILY DOPED

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19
Q

It is an atom with five valence electrons.

A

Pentavalent Atom (Donor Impurity)

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20
Q

EXAMPLES OF PENTAVALENT ATOMS (BAAP)

A

Bismuth, Arsenic (As),Antimony (Sb),

Bi) and Phosphorus (P

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21
Q

Adding Pentavalent Atom (Donor Impurity) causes conduction mainly
by means of ______

A

ELECTRON FLOW

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22
Q

It is an atom with three valence electrons.

A

Trivalent Atom (Acceptor Impurity)

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23
Q

EXAMPLES OF TRIVALENT ATOMS (BIGA)

A

Boron (B), Gallium (Ga), Indium

In) and Aluminum (Al

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24
Q

Adding TRIVALENT ATOMS causes conduction

mainly by means of _____ flow

A

HOLE

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25
Q

t is the result of adding donor impurities.

A

N-Type Material

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26
Q

Majority carriers are electrons.

• Minority carriers are holes.

A

N-Type Material

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27
Q

It is the result of adding acceptor impurities.

A

P-Type Material

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28
Q

TWO TYPES OF EXTRINSIC SEMICON

A

NTYPE AND PTYPE

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29
Q

When a voltage is applied across a piece of intrinsic
semiconductor, the thermally generated free electrons in
the conduction band, which are free to move randomly in
the crystal structure, are now easily attracted towards the
positive end.. WHAT TYPE OF CURRENT

A

ELECTRON CURRENT

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30
Q

Another type of current which occurs in the valence

band, where the holes created by the free electrons exist.

A

HOLE CURENT

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31
Q

ELECTRON CURRENT OCCURS IN ____ BAND

A

CONDUCTION

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32
Q

HOLE CURRENT OCCURS IN ____ BAND

A

VALENCE

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33
Q

It is the rate at which an electron, under the influence of
an electric field, travels at a certain distance at a certain
time.

A

Drift Velocity

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34
Q

It is the total charge passing through any area

per unit time.

A

CURRENT

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35
Q

It is the electric current per unit area.

A

Current Density, J

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36
Q

It is the number of electrons per unit volume.

A

Electron Concentration, η

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37
Q

It is the measure of electric charge per unit

volume.

A

Volume Charge Density,

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38
Q

It is a measure of the material’s ability to conduct

an electric current.

A

Conductivity or Specific Conductance

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39
Q

It is a measure of how strongly a material

opposes the flow electric current.

A

Resistivity or Specific Resistance,

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40
Q

It is the opposition to the passage of an electric

current through that element.

A

Resistance, R

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41
Q

It states that the current through a conductor between
two points is directly proportional to the potential
difference across the two points.

A

OHM’S LAW

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42
Q

Under thermal equilibrium, the product of the free
negative and positive concentration is a constant
independent of the amount of impurity doping.

A

MASS ACTION LAW

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43
Q

VALUE OF BOLTZMANN’S CONSTANT

A

8.62x10^-5 eV/K

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44
Q

It states that the total positive charge is equal to the

total negative charge.

A

Law of Electrical Neutrality

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45
Q

It is formed when an n-type and a p-type materials

are brought together.

A

PN JUNCTION

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46
Q

It is formed at the boundary between the two

regions.

A

PN JUNCTION

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47
Q

formed by doping one half of
intrinsic Si or Ge with a p-type dopant and the
other half with an n-type dopant.

A

PN JUNCTION DIODE

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48
Q

It is a two-terminal electric component that
conducts electric current in only one direction,
functioning as a one-way valve

A

PN JUNCTION DIODE

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49
Q

Because the diode is a continuous crystal,
free electrons can move across the junction.
˜When it is manufactured, some of these
electrons cross the junction to fill some of
the holes.
˜The result is that a _______ is
formed.
Electronics

A

DEPLETION REGION

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50
Q

The term _______refers to the fact that the
region near the PN junction is depleted of
charge carriers (both electrons and holes) due
to diffusion across the junction.

A

depletion

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51
Q

is the potential difference of

the electric field across the depletion region.

A

Barrier Potential

52
Q

the amount of energy required to move

the free electrons through the electric field.

A

Barrier Potential

53
Q

The typical values of barrier potential are
___ V for Silicon and ____ V for Germanium
at 25oC or 27oC (room temperature).

A

0.7 AND 0.3

54
Q

FACTORS AFFECTING BARRIER POTENTIAL (TAT)

A

1) Type of semiconductive material
2) Amount of doping
3) Temperature

55
Q

electrons move through the PN junction at

equilibrium; T OR F

A

FALSE

56
Q

there is no electrical current

through the PN junction. T OR F

A

TRUE

57
Q

refers to the use of a dc voltage to
establish certain operating conditions for an
electronic device.

A

BIAS

58
Q

It is the condition when the anode is more

positive than the cathode.

A

FORWARD BIAS

59
Q

The positive terminal of the battery repels the
holes on the p-type side and pushes them
toward the junction.

A

FORWARD BIAS

60
Q

The negative terminal of the battery repels the

electrons and pushes them toward the junction.

A

FORWARD BIAS

61
Q

This removes the depletion region WHAT TYPE OF BIAS

A

FORWARD BIAS

62
Q

It is the condition when the anode is more

negative than the cathode.

A

REVERSE BIAS

63
Q

The positive terminal of the battery applied to
the n-type material attracts the free electrons
away from the junction

A

REVERSE BIAS

64
Q

This makes the depletion region wider than it

was when no voltage was applied.

A

REVERSE BIAS

65
Q

Since the depletion region widens, it can be

expected that current will FLOW IN REVERSE BIAS ( T OR F)

A

FALSE

66
Q

The reverse bias voltage forces the minority

carriers to drift across the junction and cause _______

A

SMALL LEAKAGE CURRENT OR REVERSE CURRENT

67
Q

IN REVERSE BIAS, Actually, a small current will flow because of
the _______

A

minority carriers.

68
Q

voltage wherein the sudden increase in

current starts

A

KNEE VOLTAGE

69
Q

It is the maximum voltage that can be handled
by the junction diode.
– It is also known as the

A

Breakdown Voltage

70
Q

It is also known as the peak reverse voltage or

peak inverse voltage.

A

Breakdown Voltage

71
Q

Silicon has ______ breakdown voltage than

Germanium.

A

HIGHER

72
Q

If the external reverse-bias is increased to a value called
the breakdown voltage, the reverse current will
drastically _______.

A

increase

73
Q

This multiplication of conduction electrons is known as
______ and results in a very high reverse current
that can damage the PN structure because of excessive
heat dissipation.

A

avalanche

74
Q

It is the resistance of the diode at the quiescent

operating point.

A

DC or Static Resistance

75
Q

means “still” or “unvarying”

A

Quiescent

76
Q

In general, the higher the current through a diode, the

_____ is the dc resistance level.

A

lower

77
Q

Unlike a linear resistance, the resistance of a forwardbiased
diode is _____over the entire curve.

A

not constant

78
Q

Because the resistance changes as you move along the

V-I curve, it is called _______ resistance

A

dynamic

79
Q

is the resistance associated
with the device when a large signal is used as an
input to produce a broad swing.

A

average ac resistance

80
Q

To determine this value, a straight line is drawn
between two intersections established by the
maximum and minimum values of input voltage.

A

average ac resistance

81
Q

Electronic devices are inherently sensitive to

very high _____

A

frequencies.

82
Q

In the PN junction diode, there are two
capacitive effects to be considered.
Electronics. ENUMERATE

A

Transition-Region or Depletion-Region
Capacitance (CT)

Diffusion or Storage Capacitance (CD)

83
Q

capacitance considered in the reversebias

region

A

Transition-Region or Depletion-Region

Capacitance (CT)

84
Q

capacitance considered in the forwardbias

region

A

Diffusion or Storage Capacitance (CD)

85
Q

Diode capacitance depends on the following:

A

– Operating Voltage (Reverse-Bias Condition)
– Type of semiconductor material
– Cross-sectional area of the junction

86
Q

is a combination of circuit elements that best
represents the actual characteristics of a
semiconductor diode under a specific operating
condition.

A

diode equivalent model or equivalent circuit

87
Q

approximates the actual behavior of a
practical semiconductor diode by representing it as a
simple switch.

A

IDEAL DIODE MODEL (First Approximation)

88
Q

When the turn-on voltage is very small compared to
other voltages in the circuit and the diode’s resistance is
negligible compared to the other resistances in the
circuit, the ideal diode model may be used.

A

IDEAL DIODE MODEL (First Approximation)

89
Q

The diode when forward-biased has some threshold
voltage and has no resistance.
– When reverse-biased, it is still an open circuit.

A

SIMPLIFIED DIODE MODEL (Second

Approximation)

90
Q

The diode when forward-biased has some threshold
voltage and resistance.
– But when it is reverse-biased, it is still an open circuit.
Electronics Engineering

A

PIECEWISE LINEAR DIODE MODEL (Third

Approximation)

91
Q

MOST COMMON APPROXIMATION

A

THIRD APPROX.

92
Q

is a special kind of diode which allows
current to flow in the forward direction in the same
manner as an ideal diode, but will also permit it to flow
in the reverse direction when the voltage is above a
certain value

A

Zener diode

93
Q

zener diode was named after _____, who

discovered this electrical property.

A

Clarence Zener

94
Q

The breakdown voltage of a zener diode is set by
carefully____________during
manufacture.

A

controlling the doping level

95
Q

Recall that when a diode reaches ____, its
voltage remains almost _____even though the
current changes drastically, and this is the key to the
zener diode operation.

A

reverse breakdown

constant

96
Q

Zener diodes are designed to operate in _____

breakdown.

A

reverse

97
Q

Two Types of Reverse Breakdown

A

Avalanche Breakdown

Zener Breakdown

98
Q

_____ effect occurs at a sufficiently high reverse voltages

A

Avalance

99
Q

Zener breakdown occurs in a zener diode at ______

voltages.

A

low reverse

100
Q

A Zener diode is ____ to reduce the

breakdown voltage.

A

heavily doped

101
Q

there is a very ___ depletion region in zener diode

A

thin

102
Q

Zener diodes with breakdown voltages of less than

approximately 5V operate predominantly in _______ breakdown.

A

zener

breakdown.

103
Q

Those with breakdown voltages greater than
approximately 5V operate predominantly in _______
breakdown.

A

avalanche

104
Q

A ______ is a diode that always operates in reversebias
and is doped to maximize the inherent capacitance
of the depletion region.

A

varactor

105
Q

Varactor diodes are specially designed to take advantage
of the _______ and are used as _______
capacitors.

A

junction capacitance

voltage controlled

106
Q

The _______acts as a capacitor dielectric

because of its nonconductive characteristic.

A

depletion region

107
Q

The __ and ___ regions are conductive and act as the

capacitor plates.

A

p, n

108
Q

A ____ is a semiconductor light

source.

A

light-emitting diode (LED)

109
Q

When the device is forward-biased, electrons cross the
pn junction from the n-type material and recombine
with holes in the p-type material.

A

light-emitting diode (LED)

110
Q

in LEDs, When recombination takes place, the recombining

electrons release energy in the form of _____

A

photons

111
Q

In LEDs, a large exposed surface area on one layer of the
semiconductive material permits the photons to be
emitted as visible light.
˜ This process is called __________.

A

electroluminescence

112
Q

In LEDs, various impurities are added during the doping process
to establish the wavelength of the emitted light.
˜ The wavelength determines the _____of the visible light.

A

color

113
Q

color with highest wavelength

A

red

114
Q

color with lowest wavelength

A

violet

115
Q

color with lowest photon energy

A

red

116
Q

A _______ is a device that operates in reverse bias.

A

photodiode

117
Q

It has a small transparent window that allows light to

strike the pn junction.

A

photodiode

118
Q

When a photon of sufficient energy strikes the diode, it
excites an electron, thereby creating a free electron
(and a positively charged electron hole).
n This mechanism is also known as the _______

A

inner photoelectric

effect.

119
Q

_______diodes are high-current diodes used primarily

in high-frequency and fast-switching applications.

A

schottky

120
Q

They are also known as hot-carrier diodes.

A

schottky

121
Q

It is formed by joining a doped semiconductor region
(usually n-type) with a metal such as gold, silver, or
platinum.

A

schottky

122
Q

The ______diode operates only with majority carriers.

A

Schottky

123
Q

There are no minority carriers and thus no reverse

leakage current as in other types of diodes. WHAT DIODE

A

Schottky

124
Q

The ___diode consists of heavily doped p and n regions

separated by an intrinsic (i) region.

A

pin

125
Q

When reverse-biased, the pin diode acts like a nearly

constant _______

A

capacitance

126
Q

When forward-biased, pin diode acts like a _______

variable resistance.

A

current-controlled

127
Q

what are the diode-equivalent models? with approximation indication

A

Ideal diode model (frst approx)
simplified diode model (second apprx)
piecewise linear diode model (3rd approx)

ELECS (4 decks)

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