Understanding Kirchhoff's Current Law in Industrial Electronics

Industrial Electronics
N4
 
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Kirchhoff’s Current Law states that the algebraic sum of currents entering
a point will be equal to the algebraic sum of the currents leaving that point.
Kirchhoff’s Voltage Law states that the algebraic sum of the individual
voltage drops in a closed network is equal to the algebraic sum of the
applied voltage.
 
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In setting up two equations you must understand that theory will form the
basis. Furthermore, the concepts of Ohm’s Law are equally applicable since
Kirchhoff’s Laws has as origin Ohm’s Law.
 
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I
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The Superposition Theorem states that all current magnitudes and directions
may be determined by considering each supply on its own.
 
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The current will divide between the two resistors and will always take the
path of least resistance.
The voltage will divide between the two resistors and the largest resistor
will also have the largest voltage drop.
 
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Thevenin’s Theorem specifies that a complex network consisting of
impedances and voltage sources may be replaced by a constant voltage
source with a series impedance.
 
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It is however important that you must have a thorough background of Ohm’s
Law since Thevenin’s Theorem has that law as basis.
 
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Below we see:
A resistor connected across an alternating current supply (a);
A graphical representation of the phase relationship between the current
and the supply voltage (b); and
A phasor diagram 
(c).
 
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Below we see:
An inductor connected across an alternating current supply (a);
A graphical representation of the phase relationship between the current
and the supply voltage (b); and
A phasor diagram 
(c).
 
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Below we see:
A capacitor connected across an alternating current supply (a);
A graphical representation of the phase relationship between the current
and the supply voltage (b); and
A phasor diagram 
(c).
 
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This is a network consisting of an inductor and resistor connected in series.
 
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This is a network consisting of a capacitor and resistor connected in series.
 
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This is a network consisting of a resistor, capacitor and inductor connected in
series.
 
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This is a network consisting of an inductor and resistor connected in parallel.
 
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This is a network consisting of a capacitor and resistor connected in parallel.
 
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This is a network consisting a resistor, capacitor and inductor connected in
parallel.
 
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A more practical parallel network is illustrated below and is termed a ‘tuned
network’ or a ‘tank circuit’.
 
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C
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Complex notation is a method used to calculate different quantities in
alternating current networks in modulus and angle form which gives us a
much easier method of calculation.
 
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Matter may be defined as anything that has mass and that occupies space
and can be composed of elementary substances that are found in nature.
Matter can be divided into the following groups:
Solids;
Liquids;
Gasses; and
Plasma.
 
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A
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An atom may be defined as the smallest part of an element that can
participate in a normal chemical reaction. All atoms consist of minute
particles of electrical charges arranged in a set pattern and consist of:
Electrons;
Protons; and
Neutrons.
 
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In the diagram, the centre circle represents the nucleus consisting of the
protons and neutrons and the outer circle or circles indicates the shells for
the orbiting electrons.
 
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V
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The number of electrons in the outer shell of an atom, called the valence
shell, will determine the valency of that element. Valency is an indication of
the ability of an atom to gain or lose electrons and will determine the
electrical properties of that element.
 
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C
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Movement of electrons or conduction can and will take place in any given
conducting material, in a desired direction, should a source of power be
applied across such material. The conduction process can be by either hole
flow (transfer) or electron motion or by both.
 
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E
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In any given material, conducting or insulating, there are two distinct energy
bands in which electrons may exist, namely the conduction band and the
valence band but they will be separated by the forbidden gap.
 
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I
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U
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There are two main elements that are used in the manufacture of semi-
conductor devices or components namely Silicon and Germanium. As the
name Semi-conductor suggests, it is not a very good conductor and
something needs to be done in order to improve on its conducting
capabilities.
 
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In the diagram, the circles represent the
nucleus of the atom and the squares
indicate the valence electrons in the
valence shell. This type of crystal lattice
structure is found in all crystalline
elements.
 
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D
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Donor doping is a mixing process that will generate a free (extra) electron in
the conduction band of the atom as well as crystal lattice structure.
 
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Acceptor doping is a mixing process that will generate a hole in the
conduction band of the atom as well as crystal lattice structure.
 
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F
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The Fermi-level may be defined as the amount of energy the free electrons
as well as the holes possess within the material.
 
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T
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C
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I
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N
A PN-junction is formed when a P-type material and an N-type material is
joined together. This joining together is not an electrical junction but is a
junction which is achieved through a manufacturing process in which
electrons and holes are uniformly distributed in the two types of material
provided they have been doped to the same extent.
 
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I
N
T
R
O
D
U
C
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I
O
N
A diode may be defined a single PN-junction two terminal device which will
offer a low resistance when forward biased and a high resistance when
reverse biased.
 
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The characteristic curve is depicted below:
 
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A
 
D
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Rating factors will assist during the design phase of circuits so that reliable
as well as satisfactory operation can be assured. They can be seen as:
Low current - Up to 49 ampere;
Medium current - 50 ampere to 199 ampere; and
High current - 200 ampere and higher.
 
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E
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D
E
The electrical characteristics of a diode are based on the absolute maximum
rating system and provide information pertaining to the maximum values that
may not be exceeded for a given diode. These specifications are always
contained in the manufacturers’ specification sheets.
 
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n
t
i
n
u
e
d
)
 
T
H
E
 
D
I
O
D
E
 
L
O
A
D
-
L
I
N
E
The load-line for a diode is obtained by considering the maximum values of
forward current and the maximum value of the forward bias for a particular
rectifier diode.
 
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A
P
P
L
I
C
A
T
I
O
N
 
O
F
 
D
I
O
D
E
S
Diodes have applications such as:
Clippers; and
Rectifiers.
 
C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
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C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
R
E
C
T
I
F
I
E
R
 
C
O
N
C
E
P
T
S
There are a number of concepts that will determine the magnitude of the
output obtained from a rectifier. These are:
The transformer ratio;
Average dc-voltage;
Ripple voltage;
Ripple factor; and
PIV-rating.
 
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C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
F
I
L
T
E
R
 
N
E
T
W
O
R
K
S
A filter can be defined as a component that will remove the ripple (pulsating)
component from the output of a rectifier circuit.
 
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C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
N
O
-
L
O
A
D
 
V
O
L
T
A
G
E
The no-load voltage of any power supply may be defined as that voltage
which is supplied by the secondary winding of the transformer when the load
to that power supply is not connected.
 
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C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
V
O
L
T
A
G
E
 
R
E
G
U
L
A
T
I
O
N
Voltage regulation may be defined as that change in the output voltage (full-
load) for varying load conditions.
 
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C
h
a
p
t
e
r
 
1
0
 
 
D
i
o
d
e
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
V
O
L
T
A
G
E
 
M
A
N
I
P
U
L
A
T
I
O
N
At times, greater voltages are required and for this purpose we make use of
voltage multiplication circuits which may, depending on the design, supply
two or more times the peak input value as an output.
 
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T
H
E
 
Z
E
N
E
R
 
D
I
O
D
E
The zener diode is constructed so that it is mainly used in the reverse bias
mode. When operated in the forward bias mode, however, its forward
characteristics are similar to that of an ordinary junction diode.
 
C
h
a
p
t
e
r
 
1
1
 
 
S
p
e
c
i
a
l
 
D
i
o
d
e
s
 
a
n
d
 
A
p
p
l
i
c
a
t
i
o
n
s
 
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C
h
a
p
t
e
r
 
1
1
 
 
S
p
e
c
i
a
l
 
D
i
o
d
e
s
 
a
n
d
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
V
A
R
A
C
T
O
R
 
D
I
O
D
E
The varactor diodes are semi-conductor, voltage-dependent, variable
capacitors. Their mode of operation is determined by the capacitance that
exists at the PN-junction when the device is reversed biased.
 
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C
h
a
p
t
e
r
 
1
1
 
 
S
p
e
c
i
a
l
 
D
i
o
d
e
s
 
a
n
d
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
T
U
N
N
E
L
 
D
I
O
D
E
The tunnel diode is also termed an Esaki diode. It is also a two-terminal
device and is almost exclusively used as a high-frequency component in the
following applications:
An amplifier;
An oscillator; and
A switch.
 
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C
h
a
p
t
e
r
 
1
1
 
 
S
p
e
c
i
a
l
 
D
i
o
d
e
s
 
a
n
d
 
A
p
p
l
i
c
a
t
i
o
n
s
 
(
c
o
n
t
i
n
u
e
d
)
 
P
H
O
T
O
-
D
I
O
D
E
S
A photo-diode is a semi-conductor PN-junction device whose area of
operation is restricted to the reverse bias region.
 
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I
N
T
R
O
D
U
C
T
I
O
N
The transistor is a three-terminal two junction component and is commonly
referred to as a ‘junction transistor’ but it must be noted that there are other
types of transistors also available.
 
C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
www.futuremanagers.com
 
C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
T
R
A
N
S
I
S
T
O
R
The junction transistor consists of two types of extrinsic or doped semi-
conductor material. It has three terminals and one type of doped material (N-
or P-type) sandwiched between two types of the other type of doped material
(N-or P-type). This arrangement provides us with the opportunity of obtaining
two types of transistors namely an NPN- or PNP-transistor.
 
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C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
O
P
E
R
A
T
I
N
G
 
R
E
G
I
O
N
S
 
O
F
 
A
 
T
R
A
N
S
I
S
T
O
R
The cut-off region is that region where the emitter-base as well as the
collector-base junctions is reverse biased.
The active region is that region where the emitter-base junction is forward
biased and the collector-base junction is reverse biased.
The saturation region is that region where the emitter-base as well as the
collector-base junctions is forward biased.
 
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C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
S
W
I
T
C
H
I
N
G
 
S
P
E
E
D
 
O
F
 
A
 
T
R
A
N
S
I
S
T
O
R
Response is not always immediate when an input current is applied to the
base of a transistor since the electrons have, what is termed a ‘transit time’,
to move across the junction as well as the junction capacitance to overcome.
This rise time may be defined as the time it takes for the collector current to
rise from 10% of its maximum value to 90% of its maximum value.
 
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C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
T
R
A
N
S
I
S
T
O
R
 
A
S
 
A
 
S
W
I
T
C
H
A transistor can be utilised as an electronic switch as seen in the following
diagram:
 
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C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
T
R
A
N
S
I
S
T
O
R
 
A
S
 
A
N
 
A
M
P
L
I
F
I
E
R
The three configurations or modes of amplifier operation are:
Common emitter;
Common base; and
Common collector (emitter follower).
 
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C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
www.futuremanagers.com
 
C
h
a
p
t
e
r
 
1
2
 
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
C
O
M
M
O
N
 
E
M
I
T
T
E
R
 
G
R
A
P
H
I
C
A
L
 
A
N
A
L
Y
S
I
S
The common emitter has three main characteristic curves which defines its
behaviour. It will be possible to determine the transistor operation for static
as well as dynamic conditions. These are the:
Input characteristics;
Transfer characteristics; and
Output characteristics.
 
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I
N
T
R
O
D
U
C
T
I
O
N
All amplifiers fall into a specific category of amplification which is dependant
upon the application of the amplifier as well as the coupling method used.
The class of amplification refers to the conduction period of the output signal
compared to the input signal.
 
C
h
a
p
t
e
r
 
1
3
 
 
A
m
p
l
i
f
i
c
a
t
i
o
n
 
C
l
a
s
s
e
s
,
 
C
o
u
p
l
i
n
g
M
e
t
h
o
d
s
 
a
n
d
 
F
e
e
d
b
a
c
k
 
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C
h
a
p
t
e
r
 
1
3
 
 
A
m
p
l
i
f
i
c
a
t
i
o
n
 
C
l
a
s
s
e
s
,
 
C
o
u
p
l
i
n
g
 
M
e
t
h
o
d
s
 
a
n
d
 
F
e
e
d
b
a
c
k
(
c
o
n
t
i
n
u
e
d
)
 
C
L
A
S
S
E
S
 
O
F
 
A
M
P
L
I
F
I
C
A
T
I
O
N
There is:
Class A amplification;
Class B amplification;
Class AB amplification; and
Class C amplification.
 
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C
h
a
p
t
e
r
 
1
3
 
 
A
m
p
l
i
f
i
c
a
t
i
o
n
 
C
l
a
s
s
e
s
,
 
C
o
u
p
l
i
n
g
 
M
e
t
h
o
d
s
 
a
n
d
 
F
e
e
d
b
a
c
k
(
c
o
n
t
i
n
u
e
d
)
 
A
M
P
L
I
F
I
E
R
 
C
O
U
P
L
I
N
G
 
M
E
T
H
O
D
S
It is sometimes required to connect two or more transistors in cascade in
order to increase the gain since one transistor may not supply the required
gain on its own. This can happen through:
RC-inter-stage coupling;
Direct inter-stage coupling;
Transformer inter-stage coupling; and
Pull-pull amplifiers.
 
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C
h
a
p
t
e
r
 
1
3
 
 
A
m
p
l
i
f
i
c
a
t
i
o
n
 
C
l
a
s
s
e
s
,
 
C
o
u
p
l
i
n
g
 
M
e
t
h
o
d
s
 
a
n
d
 
F
e
e
d
b
a
c
k
(
c
o
n
t
i
n
u
e
d
)
 
C
R
O
S
S
-
O
V
E
R
 
D
I
S
T
O
R
T
I
O
N
Distortion may be defined as a condition that will occur when the output
waveform is not an amplified version of the input waveform.
 
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C
h
a
p
t
e
r
 
1
3
 
 
A
m
p
l
i
f
i
c
a
t
i
o
n
 
C
l
a
s
s
e
s
,
 
C
o
u
p
l
i
n
g
 
M
e
t
h
o
d
s
 
a
n
d
 
F
e
e
d
b
a
c
k
(
c
o
n
t
i
n
u
e
d
)
 
F
E
E
D
B
A
C
K
Feedback can be defined as a process whereby a part of the output signal is
fed back to the input in anti-phase so as to stabilise the gain of the amplifier
or similar circuit.
 
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I
N
T
R
O
D
U
C
T
I
O
N
Any transistor has a relation to current, voltage and impedance and is very
often referred to the parameters of the transistor. ‘Hybrid-parameters’ literally
means ‘of mixed origin’.
 
C
h
a
p
t
e
r
 
1
4
 
 
H
y
b
r
i
d
-
P
a
r
a
m
e
t
e
r
s
 
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C
h
a
p
t
e
r
 
1
4
 
 
H
y
b
r
i
d
-
P
a
r
a
m
e
t
e
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
T
R
A
N
S
I
S
T
O
R
 
A
S
 
A
 
T
W
O
-
P
O
R
T
 
D
E
V
I
C
E
The treatment of ac-analysis will be done in a manner that makes no
distinction between an NPN and PNP transistor. This is depicted below:
 
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C
h
a
p
t
e
r
 
1
4
 
 
H
y
b
r
i
d
-
P
a
r
a
m
e
t
e
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
S
M
A
L
L
 
S
I
G
N
A
L
 
A
N
A
L
Y
S
I
S
 
(
C
O
M
M
O
N
 
E
M
I
T
T
E
R
)
All amplifiers are basically two-port devices in that it will consist of two input
terminals and two output terminals.
 
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I
N
T
R
O
D
U
C
T
I
O
N
The Uni-Junction Transistor is mainly used in digital circuits and for the firing
circuits in SCR-Control (Silicon Controlled Rectifier).
 
C
h
a
p
t
e
r
 
1
5
 
 
U
n
i
-
J
u
n
c
t
i
o
n
 
a
n
d
 
F
i
e
l
d
 
E
f
f
e
c
t
T
r
a
n
s
i
s
t
o
r
s
 
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C
h
a
p
t
e
r
 
1
5
 
 
U
n
i
-
J
u
n
c
t
i
o
n
 
a
n
d
 
F
i
e
l
d
 
E
f
f
e
c
t
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
U
J
T
-
T
R
A
N
S
I
S
T
O
R
The construction of a UJT-transistor consists of a
piece of N-type silicon material on which a heavily doped P-type material is
attached and is termed the emitter. The UJT is a three-terminal device but
only contains one PN-junction.
 
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C
h
a
p
t
e
r
 
1
5
 
 
U
n
i
-
J
u
n
c
t
i
o
n
 
a
n
d
 
F
i
e
l
d
 
E
f
f
e
c
t
 
T
r
a
n
s
i
s
t
o
r
s
 
(
c
o
n
t
i
n
u
e
d
)
 
F
I
E
L
D
 
E
F
F
E
C
T
 
T
R
A
N
S
I
S
T
O
R
These have the following characteristics over bi-polar transistors:
No off-set voltage when used as a switch;
Small gain-bandwidth;
Low noise level;
Relatively immune to radiation;
Extremely high input impedance; and
Good thermal stability.
 
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I
N
T
R
O
D
U
C
T
I
O
N
Power control forms an integral part in the electronic as well as electric field
in modern industry today.
 
C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
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C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
S
I
L
I
C
O
N
 
C
O
N
T
R
O
L
L
E
D
 
R
E
C
T
I
F
I
E
R
An SCR may be defined as an ordinary diode with a control element namely
the gate.
 
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C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
(
c
o
n
t
i
n
u
e
d
)
 
D
E
L
A
Y
 
A
N
G
L
E
 
A
N
D
 
C
O
N
D
U
C
T
I
O
N
 
A
N
G
L
E
The delay angle may be defined as that part of the waveform for which no
conduction will take place whereas the conduction angle may be defined as
that part of the waveform for which conduction will take place.
 
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C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
(
c
o
n
t
i
n
u
e
d
)
 
S
C
R
 
A
P
P
L
I
C
A
T
I
O
N
S
SCR may be used for speed control or for a light dimmer.
 
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C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
(
c
o
n
t
i
n
u
e
d
)
 
S
C
R
 
C
O
N
T
R
O
L
 
M
E
T
H
O
D
S
These include:
Phase control;
Cycle control;
Cyclotronic control; and
Duty control.
 
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C
h
a
p
t
e
r
 
1
6
 
 
P
o
w
e
r
 
C
o
n
t
r
o
l
 
(
c
o
n
t
i
n
u
e
d
)
 
T
H
E
 
D
I
A
C
A Diac is a two terminal bi-directional semi-conductor component which is
normally used in conjunction with a Triac. A Diac can conduct in both
directions and may be seen as two diodes connected back-to-back.
 
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A Triac is a three terminal bi-directional gate-controlled semi-conductor
component which is normally used in conjunction with a Diac. This
component has the advantage that it may be triggered by a positive pulse on
the gate for one half of the input waveform as well as a negative pulse on the
other half of the input waveform thereby giving us full-wave control in a single
component.
 
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Using a Diac and a Triac gives us the opportunity to make use of full-wave
control. The purpose of the diac is mainly to allow a negative pulse on the
gate during the negative half of the input waveform and to allow a positive
pulse on the gate during the positive half of the input waveform.
 
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A Quadrac is a three terminal bi-directional semi-conductor component and
consists of a Diac and a Triac in one package and has the characteristics of
each component on its own.
 
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There are two types of main control systems available in industry today:
Open-loop control systems; and
Closed-loop control systems.
 
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All circuits have to be constructed using discreet components (transistors,
resistors, capacitors, inductors, diodes, etc.) and that it is quite a
cumbersome effort. The operational amplifier solves this problem to quite an
extent in that an amplifier is now available in a single integrated circuit (IC)
package.
 
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Various modes of operation can be obtained from an operational amplifier
and the operation is based on the concept of a differential amplifier.
An operational amplifier has two input terminals namely an inverting input
marked - and a non-inverting input marked +. A single output can be
obtained depending on which of the above terminals have been utilised as
the input.
 
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The good characteristics, size and cost of operational amplifiers makes them
very versatile in a number of applications, such as:
The inverting amplifier;
The non-inverting amplifier;
The inverting summing amplifier; and
The voltage follower.
 
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Operational amplifiers can be used for mathematical decision making
applications such as:
The differentiator; and
The integrator.
 
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In the field of Electronics it is required that use is made of different test
instruments to perform our task. Some of these instruments are used to
provide specific quantities such as the function generator and other
instruments are used to be able to measure, but more so to observe such as
the oscilloscope.
 
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A function generator is an instrument that is capable of delivering a choice of
waveforms and whose frequencies are adjustable over a fairly large range.
The output wave forms available include:
Sine waves;
Triangular waves;
Square waves; and
Saw-tooth waves from terminals A, B and C.
 
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An oscilloscope is a measuring instrument which is not only capable of giving
the magnitude of a measurement but also the shape of the variable. It may
be used in the following applications:
Studying waveforms and indicating phase relationships of waveforms;
Ac- and dc-voltage measurement;
Amplification gain;
Frequency determination and/or distortion indication.
 
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The signal to be studied and the time base signal must be synchronised in
order to ensure a stable signal on the oscilloscope screen.
 
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We need to consider the layout of the CRT-screen:
 
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During the process of utilising test instruments such as oscilloscopes and
function generators one will meet up with various forms of waves such as
sine-waves.
 
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A transducer can be defined as a device that converts one form of energy
into another form of energy.
 
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There are numerous types of transducers available for use. The following
criteria need to be taken into account when selecting a transducer:
Determine the physical quantity that needs to be measured.
Which transducer principle is best suited to measure a particular quantity?
What is the level of accuracy that will be required for this measurement?
 
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There are the following applications possible:
Mechanical transducers; and
Electrical transducers.
 
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The capacitor is most commonly used include the following:
Air;
Mica;
Paper;
Ceramic; and
Electrolytic and each material will have its own given dielectric constant.
 
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Inductive transducers make use of a change in magnetic field characteristics
since it is impossible to alter the inductance value of the inductor.
 
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Semi-conductors exhibits the phenomena to change its characteristics when
exposed to light whether it be natural light or artificial light hence the term
‘photosensitive’ which literally translates to being sensitive to light.
 
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It is possible to generate a voltage by means of a thermo-couple. A thermo
couple consists of two dissimilar metal wires joined at one end termed the
sensing or hot junction and terminated at the other end termed the reference
or cold junction.
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Kirchhoff's Current Law in industrial electronics states that the total current flowing into a point is equal to the total current flowing out of that point. This fundamental principle is essential for analyzing and designing electrical circuits, ensuring the conservation of current flow at any junction.


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  1. Industrial Electronics N4

  2. Chapter 1 Kirchhoff's Law KIRCHHOFF S LAWS Kirchhoff s Current Law states that the algebraic sum of currents entering a point will be equal to the algebraic sum of the currents leaving that point. Kirchhoff s Voltage Law states that the algebraic sum of the individual voltage drops in a closed network is equal to the algebraic sum of the applied voltage. www.futuremanagers.com

  3. Chapter 1 Kirchhoff's Law (continued) APPLICATION OF KIRCHHOFF S LAWS In setting up two equations you must understand that theory will form the basis. Furthermore, the concepts of Ohm s Law are equally applicable since Kirchhoff s Laws has as origin Ohm s Law. www.futuremanagers.com

  4. Chapter 2 Superposition Theorem INTRODUCTION The Superposition Theorem states that all current magnitudes and directions may be determined by considering each supply on its own. www.futuremanagers.com

  5. Chapter 2 Superposition Theorem (continued) CURRENT- AND VOLTAGE DIVISION The current will divide between the two resistors and will always take the path of least resistance. The voltage will divide between the two resistors and the largest resistor will also have the largest voltage drop. www.futuremanagers.com

  6. Chapter 3 Thevenins Theorem INTRODUCTION Thevenin s Theorem specifies that a complex network consisting of impedances and voltage sources may be replaced by a constant voltage source with a series impedance. www.futuremanagers.com

  7. Chapter 3 Thevenins Theorem (continued) APPLICATION OF THEVENIN S THEOREM It is however important that you must have a thorough background of Ohm s Law since Thevenin s Theorem has that law as basis. www.futuremanagers.com

  8. Chapter 4 Series RLC-networks THE EFFECT OF AN ALTERNATING QUANTITY ON A RESISTOR Below we see: A resistor connected across an alternating current supply (a); A graphical representation of the phase relationship between the current and the supply voltage (b); and A phasor diagram (c). www.futuremanagers.com

  9. Chapter 4 Series RLC-networks (continued) THE EFFECT OF AN ALTERNATING QUANTITY ON AN INDUCTOR Below we see: An inductor connected across an alternating current supply (a); A graphical representation of the phase relationship between the current and the supply voltage (b); and A phasor diagram (c). www.futuremanagers.com

  10. Chapter 4 Series RLC-networks (continued) THE EFFECT OF AN ALTERNATING QUANTITY ON A CAPACITOR Below we see: A capacitor connected across an alternating current supply (a); A graphical representation of the phase relationship between the current and the supply voltage (b); and A phasor diagram (c). www.futuremanagers.com

  11. Chapter 4 Series RLC-networks (continued) THE SERIES R-L NETWORK This is a network consisting of an inductor and resistor connected in series. www.futuremanagers.com

  12. Chapter 4 Series RLC-networks (continued) THE SERIES R-C NETWORK This is a network consisting of a capacitor and resistor connected in series. www.futuremanagers.com

  13. Chapter 4 Series RLC-networks (continued) THE SERIES RLC-NETWORK This is a network consisting of a resistor, capacitor and inductor connected in series. www.futuremanagers.com

  14. Chapter 4 Series RLC-networks (continued) CONDITIONS FOR RESONANCE The following conditions will exist for ? = ? and is minimum resonance in a series RLC-network. ? = 0 ??= ?? ??= ?? and is maximum ??= ?? I is maximum 1 ? = 1 2 2 ? ? ? www.futuremanagers.com

  15. Chapter 5 Parallel RLC-networks THE PARALLEL RL-NETWORK This is a network consisting of an inductor and resistor connected in parallel. www.futuremanagers.com

  16. Chapter 5 Parallel RLC-networks (continued) THE PARALLEL RC-NETWORK This is a network consisting of a capacitor and resistor connected in parallel. www.futuremanagers.com

  17. Chapter 5 Parallel RLC-networks (continued) THE PARALLEL RLC-NETWORK This is a network consisting a resistor, capacitor and inductor connected in parallel. www.futuremanagers.com

  18. Chapter 5 Parallel RLC-networks (continued) CONDITIONS FOR RESONANCE The following conditions will exist for resonance in a parallel RLC-network. ? is minimum ??= ?? ??= ?? and is maximum ??= ?? ? = 0 I is minimum 1 ? = 1 2 2 ? ? ? www.futuremanagers.com

  19. Chapter 5 Parallel RLC-networks (continued) THE TUNED NETWORK A more practical parallel network is illustrated below and is termed a tuned network or a tank circuit . www.futuremanagers.com

  20. Chapter 6 Q-factor, Bandwidth and Complex Notation THE Q-FACTOR The Q-factor of a network is also termed the magnification factor and is applicable to either a series- or parallel resonant network. This factor is mathematically expressed by: ? =?? ? www.futuremanagers.com

  21. Chapter 6 Q-factor, Bandwidth and Complex Notation (continued) BANDWIDTH The bandwidth may be defined as that range of frequencies between ?1 and ?2 where the power has fallen or dropped to half its value. www.futuremanagers.com

  22. Chapter 6 Q-factor, Bandwidth and Complex Notation (continued) COMPLEX NOTATION Complex notation is a method used to calculate different quantities in alternating current networks in modulus and angle form which gives us a much easier method of calculation. www.futuremanagers.com

  23. Chapter 7 Basic Atomic Theory THE STRUCTURE OF MATTER Matter may be defined as anything that has mass and that occupies space and can be composed of elementary substances that are found in nature. Matter can be divided into the following groups: Solids; Liquids; Gasses; and Plasma. www.futuremanagers.com

  24. Chapter 7 Basic Atomic Theory (continued) ATOMS An atom may be defined as the smallest part of an element that can participate in a normal chemical reaction. All atoms consist of minute particles of electrical charges arranged in a set pattern and consist of: Electrons; Protons; and Neutrons. www.futuremanagers.com

  25. Chapter 7 Basic Atomic Theory (continued) ENERGY SHELLS In the diagram, the centre circle represents the nucleus consisting of the protons and neutrons and the outer circle or circles indicates the shells for the orbiting electrons. www.futuremanagers.com

  26. Chapter 7 Basic Atomic Theory (continued) VALENCY The number of electrons in the outer shell of an atom, called the valence shell, will determine the valency of that element. Valency is an indication of the ability of an atom to gain or lose electrons and will determine the electrical properties of that element. www.futuremanagers.com

  27. Chapter 7 Basic Atomic Theory (continued) CONDUCTION Movement of electrons or conduction can and will take place in any given conducting material, in a desired direction, should a source of power be applied across such material. The conduction process can be by either hole flow (transfer) or electron motion or by both. www.futuremanagers.com

  28. Chapter 7 Basic Atomic Theory (continued) ENERGY BANDS In any given material, conducting or insulating, there are two distinct energy bands in which electrons may exist, namely the conduction band and the valence band but they will be separated by the forbidden gap. www.futuremanagers.com

  29. Chapter 8 PN-Junction Theory INTRODUCTION There are two main elements that are used in the manufacture of semi- conductor devices or components namely Silicon and Germanium. As the name Semi-conductor suggests, it is not a very good conductor and something needs to be done in order to improve on its conducting capabilities. www.futuremanagers.com

  30. Chapter 8 PN-Junction Theory (continued) CRYSTAL LATTICE STRUCTURES In the diagram, the circles represent the nucleus of the atom and the squares indicate the valence electrons in the valence shell. This type of crystal lattice structure is found in all crystalline elements. www.futuremanagers.com

  31. Chapter 8 PN-Junction Theory (continued) DONOR DOPING Donor doping is a mixing process that will generate a free (extra) electron in the conduction band of the atom as well as crystal lattice structure. www.futuremanagers.com

  32. Chapter 8 PN-Junction Theory (continued) ACCEPTOR DOPING Acceptor doping is a mixing process that will generate a hole in the conduction band of the atom as well as crystal lattice structure. www.futuremanagers.com

  33. Chapter 8 PN-Junction Theory (continued) FERMI-LEVELS The Fermi-level may be defined as the amount of energy the free electrons as well as the holes possess within the material. www.futuremanagers.com

  34. Chapter 8 PN-Junction Theory (continued) THE PN-JUNCTION A PN-junction is formed when a P-type material and an N-type material is joined together. This joining together is not an electrical junction but is a junction which is achieved through a manufacturing process in which electrons and holes are uniformly distributed in the two types of material provided they have been doped to the same extent. www.futuremanagers.com

  35. Chapter 9 Semi-conductor Diodes INTRODUCTION A diode may be defined a single PN-junction two terminal device which will offer a low resistance when forward biased and a high resistance when reverse biased. www.futuremanagers.com

  36. Chapter 9 Semi-conductor Diodes (continued) THE DIODE AND CHARACTERISTIC CURVE The characteristic curve is depicted below: www.futuremanagers.com

  37. Chapter 9 Semi-conductor Diodes (continued) BASIC RATING FACTORS OF A DIODE Rating factors will assist during the design phase of circuits so that reliable as well as satisfactory operation can be assured. They can be seen as: Low current - Up to 49 ampere; Medium current - 50 ampere to 199 ampere; and High current - 200 ampere and higher. www.futuremanagers.com

  38. Chapter 9 Semi-conductor Diodes (continued) ELECTRICAL CHARACTERISTICS OF A DIODE The electrical characteristics of a diode are based on the absolute maximum rating system and provide information pertaining to the maximum values that may not be exceeded for a given diode. These specifications are always contained in the manufacturers specification sheets. www.futuremanagers.com

  39. Chapter 9 Semi-conductor Diodes (continued) THE DIODE EQUATION ? = ??(???/??)-1 Where i = forward current ??= reverse saturation current q = electron charge V = potential difference across the diode K = Boltzmann s constant T = temperature www.futuremanagers.com

  40. Chapter 9 Semi-conductor Diodes (continued) FORWARD RESISTANCE OF A DIODE All diodes are manufactured from semi-conductor materials and will have a resistance caused by its atomic structure. This resistance is given by: ? =? ? ? ? Where K = Boltzmann s constant T = temperature in Kelvin q = electron charge www.futuremanagers.com

  41. Chapter 9 Semi-conductor Diodes (continued) THE DIODE LOAD-LINE The load-line for a diode is obtained by considering the maximum values of forward current and the maximum value of the forward bias for a particular rectifier diode. www.futuremanagers.com

  42. Chapter 10 Diode Applications APPLICATION OF DIODES Diodes have applications such as: Clippers; and Rectifiers. www.futuremanagers.com

  43. Chapter 10 Diode Applications (continued) RECTIFIER CONCEPTS There are a number of concepts that will determine the magnitude of the output obtained from a rectifier. These are: The transformer ratio; Average dc-voltage; Ripple voltage; Ripple factor; and PIV-rating. www.futuremanagers.com

  44. Chapter 10 Diode Applications (continued) FILTER NETWORKS A filter can be defined as a component that will remove the ripple (pulsating) component from the output of a rectifier circuit. www.futuremanagers.com

  45. Chapter 10 Diode Applications (continued) NO-LOAD VOLTAGE The no-load voltage of any power supply may be defined as that voltage which is supplied by the secondary winding of the transformer when the load to that power supply is not connected. www.futuremanagers.com

  46. Chapter 10 Diode Applications (continued) VOLTAGE REGULATION Voltage regulation may be defined as that change in the output voltage (full- load) for varying load conditions. www.futuremanagers.com

  47. Chapter 10 Diode Applications (continued) VOLTAGE MANIPULATION At times, greater voltages are required and for this purpose we make use of voltage multiplication circuits which may, depending on the design, supply two or more times the peak input value as an output. www.futuremanagers.com

  48. Chapter 11 Special Diodes and Applications THE ZENER DIODE The zener diode is constructed so that it is mainly used in the reverse bias mode. When operated in the forward bias mode, however, its forward characteristics are similar to that of an ordinary junction diode. www.futuremanagers.com

  49. Chapter 11 Special Diodes and Applications (continued) THE VARACTOR DIODE The varactor diodes are semi-conductor, voltage-dependent, variable capacitors. Their mode of operation is determined by the capacitance that exists at the PN-junction when the device is reversed biased. www.futuremanagers.com

  50. Chapter 11 Special Diodes and Applications (continued) THE TUNNEL DIODE The tunnel diode is also termed an Esaki diode. It is also a two-terminal device and is almost exclusively used as a high-frequency component in the following applications: An amplifier; An oscillator; and A switch. www.futuremanagers.com

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