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
2
Q
Semiconductor materials are insulators at absolute
____temperature and conduct electricity in a
limited way at room temperature.
A
zero
3
Q
semiconductors have exactly _____ valence
electrons.
A
four
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
5
Q
The most common semiconductor materials are
_____.
A
Silicon (Si) and Germanium (Ge)
6
Q
Compound semiconductors like _______are also in common use.
A
Gallium Arsenide
(GaAs), Aluminum Arsenide (AlAs) and Gallium
Phosphide (GaP)
7
Q
It is a non-metallic element which was discovered in
1823 and found extensively in the earth’s crust.
A
SILICON
8
Q
It is a brittle, grayish-white earth element which was
discovered in 1886.
A
GERMANIUM
9
Q
Atoms in a semiconductor are arranged in
the form of a _______
A
crystal lattice.
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
11
Q
It refers to pure materials and therefore free from
impurities that exist naturally like pure silicon and
pure germanium.
A
Intrinsic Semiconductor
12
Q
It has equal numbers of negative carriers (electrons)
and positive carriers (holes).
A
Intrinsic Semiconductor
13
Q
If a voltage is applied, then both the electron and the
hole can contribute to a small current flow.
A
Intrinsic Semiconductor
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
15
Q
It is the process of adding pentavalent or trivalent
impurities to an intrinsic material in
order to increase the
A
DOPING
16
Q
ANOTHER TERM FOR pentavalent or trivalent
impurities
A
DOPANTS
17
Q
means that only few impurities are added
resulting to a higher resistance (lower conductivity)
A
LIGHTLY DOPED
18
Q
means that more impurities are added
resulting to a lower resistance (higher conductivity)
A
HEAVILY DOPED
19
Q
It is an atom with five valence electrons.
A
Pentavalent Atom (Donor Impurity)
20
Q
EXAMPLES OF PENTAVALENT ATOMS (BAAP)
A
Bismuth, Arsenic (As),Antimony (Sb),
Bi) and Phosphorus (P
21
Q
Adding Pentavalent Atom (Donor Impurity) causes conduction mainly
by means of ______
A
ELECTRON FLOW
22
Q
It is an atom with three valence electrons.
A
Trivalent Atom (Acceptor Impurity)
23
Q
EXAMPLES OF TRIVALENT ATOMS (BIGA)
A
Boron (B), Gallium (Ga), Indium
In) and Aluminum (Al
24
Q
Adding TRIVALENT ATOMS causes conduction
mainly by means of _____ flow
A
HOLE
25
t is the result of adding donor impurities.
N-Type Material
26
Majority carriers are electrons.
| • Minority carriers are holes.
N-Type Material
27
It is the result of adding acceptor impurities.
P-Type Material
28
TWO TYPES OF EXTRINSIC SEMICON
NTYPE AND PTYPE
29
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
ELECTRON CURRENT
30
Another type of current which occurs in the valence
| band, where the holes created by the free electrons exist.
HOLE CURENT
31
ELECTRON CURRENT OCCURS IN ____ BAND
CONDUCTION
32
HOLE CURRENT OCCURS IN ____ BAND
VALENCE
33
It is the rate at which an electron, under the influence of
an electric field, travels at a certain distance at a certain
time.
Drift Velocity
34
It is the total charge passing through any area
| per unit time.
CURRENT
35
It is the electric current per unit area.
Current Density, J
36
It is the number of electrons per unit volume.
Electron Concentration, η
37
It is the measure of electric charge per unit
| volume.
Volume Charge Density,
38
It is a measure of the material’s ability to conduct
| an electric current.
Conductivity or Specific Conductance
39
It is a measure of how strongly a material
| opposes the flow electric current.
Resistivity or Specific Resistance,
40
It is the opposition to the passage of an electric
| current through that element.
Resistance, R
41
It states that the current through a conductor between
two points is directly proportional to the potential
difference across the two points.
OHM'S LAW
42
Under thermal equilibrium, the product of the free
negative and positive concentration is a constant
independent of the amount of impurity doping.
MASS ACTION LAW
43
VALUE OF BOLTZMANN'S CONSTANT
8.62x10^-5 eV/K
44
It states that the total positive charge is equal to the
| total negative charge.
Law of Electrical Neutrality
45
It is formed when an n-type and a p-type materials
| are brought together.
PN JUNCTION
46
It is formed at the boundary between the two
| regions.
PN JUNCTION
47
formed by doping one half of
intrinsic Si or Ge with a p-type dopant and the
other half with an n-type dopant.
PN JUNCTION DIODE
48
It is a two-terminal electric component that
conducts electric current in only one direction,
functioning as a one-way valve
PN JUNCTION DIODE
49
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
DEPLETION REGION
50
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.
depletion
51
is the potential difference of
| the electric field across the depletion region.
Barrier Potential
52
the amount of energy required to move
| the free electrons through the electric field.
Barrier Potential
53
The typical values of barrier potential are
___ V for Silicon and ____ V for Germanium
at 25oC or 27oC (room temperature).
0.7 AND 0.3
54
FACTORS AFFECTING BARRIER POTENTIAL (TAT)
1) Type of semiconductive material
2) Amount of doping
3) Temperature
55
electrons move through the PN junction at
| equilibrium; T OR F
FALSE
56
there is no electrical current
| through the PN junction. T OR F
TRUE
57
refers to the use of a dc voltage to
establish certain operating conditions for an
electronic device.
BIAS
58
It is the condition when the anode is more
| positive than the cathode.
FORWARD BIAS
59
The positive terminal of the battery repels the
holes on the p-type side and pushes them
toward the junction.
FORWARD BIAS
60
The negative terminal of the battery repels the
| electrons and pushes them toward the junction.
FORWARD BIAS
61
This removes the depletion region WHAT TYPE OF BIAS
FORWARD BIAS
62
It is the condition when the anode is more
| negative than the cathode.
REVERSE BIAS
63
The positive terminal of the battery applied to
the n-type material attracts the free electrons
away from the junction
REVERSE BIAS
64
This makes the depletion region wider than it
| was when no voltage was applied.
REVERSE BIAS
65
Since the depletion region widens, it can be
| expected that current will FLOW IN REVERSE BIAS ( T OR F)
FALSE
66
The reverse bias voltage forces the minority
| carriers to drift across the junction and cause _______
SMALL LEAKAGE CURRENT OR REVERSE CURRENT
67
IN REVERSE BIAS, Actually, a small current will flow because of
the _______
minority carriers.
68
voltage wherein the sudden increase in
| current starts
KNEE VOLTAGE
69
It is the maximum voltage that can be handled
by the junction diode.
– It is also known as the
Breakdown Voltage
70
It is also known as the peak reverse voltage or
| peak inverse voltage.
Breakdown Voltage
71
Silicon has ______ breakdown voltage than
| Germanium.
HIGHER
72
If the external reverse-bias is increased to a value called
the breakdown voltage, the reverse current will
drastically _______.
increase
73
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.
avalanche
74
It is the resistance of the diode at the quiescent
| operating point.
DC or Static Resistance
75
means “still” or “unvarying”
Quiescent
76
In general, the higher the current through a diode, the
| _____ is the dc resistance level.
lower
77
Unlike a linear resistance, the resistance of a forwardbiased
diode is _____over the entire curve.
not constant
78
Because the resistance changes as you move along the
| V-I curve, it is called _______ resistance
dynamic
79
is the resistance associated
with the device when a large signal is used as an
input to produce a broad swing.
average ac resistance
80
To determine this value, a straight line is drawn
between two intersections established by the
maximum and minimum values of input voltage.
average ac resistance
81
Electronic devices are inherently sensitive to
| very high _____
frequencies.
82
In the PN junction diode, there are two
capacitive effects to be considered.
Electronics. ENUMERATE
Transition-Region or Depletion-Region
Capacitance (CT)
Diffusion or Storage Capacitance (CD)
83
capacitance considered in the reversebias
| region
Transition-Region or Depletion-Region
| Capacitance (CT)
84
capacitance considered in the forwardbias
| region
Diffusion or Storage Capacitance (CD)
85
Diode capacitance depends on the following:
– Operating Voltage (Reverse-Bias Condition)
– Type of semiconductor material
– Cross-sectional area of the junction
86
is a combination of circuit elements that best
represents the actual characteristics of a
semiconductor diode under a specific operating
condition.
diode equivalent model or equivalent circuit
87
approximates the actual behavior of a
practical semiconductor diode by representing it as a
simple switch.
IDEAL DIODE MODEL (First Approximation)
88
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.
IDEAL DIODE MODEL (First Approximation)
89
The diode when forward-biased has some threshold
voltage and has no resistance.
– When reverse-biased, it is still an open circuit.
SIMPLIFIED DIODE MODEL (Second
| Approximation)
90
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
PIECEWISE LINEAR DIODE MODEL (Third
| Approximation)
91
MOST COMMON APPROXIMATION
THIRD APPROX.
92
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
Zener diode
93
zener diode was named after _____, who
| discovered this electrical property.
Clarence Zener
94
The breakdown voltage of a zener diode is set by
carefully____________during
manufacture.
controlling the doping level
95
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.
reverse breakdown
| constant
96
Zener diodes are designed to operate in _____
| breakdown.
reverse
97
Two Types of Reverse Breakdown
Avalanche Breakdown
| Zener Breakdown
98
_____ effect occurs at a sufficiently high reverse voltages
Avalance
99
Zener breakdown occurs in a zener diode at ______
| voltages.
low reverse
100
A Zener diode is ____ to reduce the
| breakdown voltage.
heavily doped
101
there is a very ___ depletion region in zener diode
thin
102
Zener diodes with breakdown voltages of less than
| approximately 5V operate predominantly in _______ breakdown.
zener
| breakdown.
103
Those with breakdown voltages greater than
approximately 5V operate predominantly in _______
breakdown.
avalanche
104
A ______ is a diode that always operates in reversebias
and is doped to maximize the inherent capacitance
of the depletion region.
varactor
105
Varactor diodes are specially designed to take advantage
of the _______ and are used as _______
capacitors.
junction capacitance
| voltage controlled
106
The _______acts as a capacitor dielectric
| because of its nonconductive characteristic.
depletion region
107
The __ and ___ regions are conductive and act as the
| capacitor plates.
p, n
108
A ____ is a semiconductor light
| source.
light-emitting diode (LED)
109
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.
light-emitting diode (LED)
110
in LEDs, When recombination takes place, the recombining
| electrons release energy in the form of _____
photons
111
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 __________.
electroluminescence
112
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.
color
113
color with highest wavelength
red
114
color with lowest wavelength
violet
115
color with lowest photon energy
red
116
A _______ is a device that operates in reverse bias.
photodiode
117
It has a small transparent window that allows light to
| strike the pn junction.
photodiode
118
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 _______
inner photoelectric
| effect.
119
_______diodes are high-current diodes used primarily
| in high-frequency and fast-switching applications.
schottky
120
They are also known as hot-carrier diodes.
schottky
121
It is formed by joining a doped semiconductor region
(usually n-type) with a metal such as gold, silver, or
platinum.
schottky
122
The ______diode operates only with majority carriers.
Schottky
123
There are no minority carriers and thus no reverse
| leakage current as in other types of diodes. WHAT DIODE
Schottky
124
The ___diode consists of heavily doped p and n regions
| separated by an intrinsic (i) region.
pin
125
When reverse-biased, the pin diode acts like a nearly
| constant _______
capacitance
126
When forward-biased, pin diode acts like a _______
| variable resistance.
current-controlled
127
what are the diode-equivalent models? with approximation indication
Ideal diode model (frst approx)
simplified diode model (second apprx)
piecewise linear diode model (3rd approx)
