E-Portfolio Mohd Fardzlee bin Abd Patah GB190077 MBV

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How is a Wiring Diagram Different from a Schematic?
A schematic shows the plan and function for an electrical circuit, but is not concerned with
the physical layout of the wires. Wiring diagrams show how the wires are connected and
where they should have located in the actual device, as well as the physical connections
between all the components.
How is a Wiring Diagram Different from a Pictorial Diagram?
Unlike a pictorial diagram, a wiring diagram uses abstract or simplified shapes and lines to
show components. Pictorial diagrams are often photos with labels or highly-detailed
drawings of the physical components.
Standard Wiring Diagram Symbols
If a line touching another line has a black dot, it means the lines are connected. When
unconnected lines are shown crossing, you'll see a line hop.

Most symbols used on a wiring diagram look like abstract versions of the real objects they
represent. For example, a switch will be a break in the line with a line at an angle to the
wire, much like a light switch you can flip on and off. A resistor will be represented with a

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series of squiggles symbolizing the restriction of current flow. An antenna is a straight line
with three small lines branching off at its end, much like a real antenna.

 Wire, conducts current
 Fuse, disconnect when current exceeds a certain amount
 Capacitor, used to store electric charge
 Toggle Switch, stops the flow of current when open
 Push Button Switch, momentarily allows current flow when button is pushed in,

breaks current when released
 Battery, stores electric charge and generates a constant voltage
 Resistor, restricts current flow
 Ground wire, used for protection

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 Circuit breaker, used to protect a circuit from an overload of current
 Inductor, a coil that generates a magnetic field
 Antenna, transmits and receives radio waves
 Surge protector, used to protect a circuit from a spike in voltage
 Lamp, generates light when current flows through
 Diode, allows current to flow in one direction indicated by an arrowhead or triangle

on the wire
 Microphone, converts sound into electrical signal
 Electrical motor
 Transformer, changes AC voltage from high to low or vice versa
 Headphone
 Thermostat
 Electrical outlet
 Junction box

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WIRE CODE IDENTIFICATION
Each wire shown in the diagrams contains a code (Fig. 1) which identifies the main circuit,
part of the main circuit, gauge of wire, and color. The color is shown as a two-letter code,
which can be identified by referring to the Wire Color Code Chart (Fig. 2).

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EXERCISE:

1. What is the function of relays, solenoid and switch?
2. List down the types of connector.
3. State the function of switch and list down the types.
4. List down the type of wire and describe the function of each wire.

REFERENCE:

1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.

2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.

3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.

4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.

5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.

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Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka

INFORMATION SHEET

PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 03
ELECTRONIC FUNDAMENTAL

WEEK 12

TOPIC 3.0 Automotive Electrical System

SUB-TOPIC 3.2. Electronic components

TOPIC After the lesson, student should be able to:
LEARNING 1. Identify basic electronic components, symbols and function.
OUTCOME

Electronics is a branch of an engineering, which deals with electronic and electrical circuits
like Integrated circuits, Transmitters, and Receiver etc. The electronic circuit is defined as
it is a combination of various electronic components that allow the flow of electric current.
The electronic components consist of two or more terminals, that are used to connect one
component to another component to design a circuit diagram. The electronic components
are soldered on circuit boards to make a system. If you want to focus on core side projects
like electronics/ electrical, you should know the basic concepts of electronic circuit symbols
and their usage. This article gives an overview of electronic circuit symbols with their
functionality.

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Electronic Circuit Symbols
The electronic circuit symbols mainly involve wires, power supplies, resistors, capacitors,
diodes, transistors, meters, switches, sensors, logic gates, audio devices, and other
components.
Wires
A wire is a two terminal, single and flexible material, that allows the flow of power through
it. These are mainly used to connect the power supplies to the PCB( Printed Circuit
Board) and in between the components. The different types of wires will be as

Wires
Wires: A single wire with two terminals will pass the current from one component to
another.
Wires Jointed: When two or more wires are connected with each other that is called as
wires jointed. The joining or shorted of wires at one point is indicates the “blob”.
Wires not Jointed: In complex circuit diagrams, some wires may not connect with
others, in this case, bridging is commonly utilized.
Power Supplies
A Power supply/ power supply unit is an electronic device, that supplies electric energy to
an electrical load. The flow of an electric current will be measured in terms of Watts. The
function of the power supply is, it converts energy from one form to another according to
our requirement. The various types of power supplies are

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Power Supplies
Cell Circuit: Supplies electrical energy from larger terminal (+) positive sign.
Battery Circuit: A Battery is two or more cells, the function of battery circuit is the same
as cell circuit.
DC Circuit Symbol: Direct current (DC) always flows in one direction.
AC Circuit Symbol: AC (Alternating Current) flows periodically reverses direction.
Fuse Circuit: The fuse will flow sufficient current and it is used to provide overcurrent
protection.
Transformer: It is used to produce AC power supply, energy is transferred in between
primary and secondary coils in the form of mutual inductance.
Solar cell: It will convert light energy into electrical energy.
Earth: It supplies the 0V to the circuit that will connect to the earth.
Voltage Source: It will supply voltage to the circuit elements.
Current Source: It will supply current to the circuit elements.
AC Voltage Source: It will supply the AC voltage to the circuit elements.
Controlled Voltage Source: It generates controlled voltage to the circuit elements.
Controlled Current Source: It generates controlled current to the circuit elements.

Resistors
A Resistor is a passive element that opposes current flow in a circuit. It is a two-terminal
element, dissipates its energy in the form of heat. The resistor will damage due to the
overflow of electric current through it. Resistance is measured in units of ohms and
resistance, resistor color code calculator is used to calculate the value of the resistor
according to its colors.

Resistors
Resistor: It is a two terminal component, that restricts the flow of current.
Rheostat: It is a two terminal component, that is used to adjust the flow of current.
Potentiometer: Potentiometer is a three-terminal component that will adjust the voltage
flow in the circuit.

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Preset: Preset is a low-cost adjustable resistor that operates by using small tools like
Screwdrivers.
Capacitors
A Capacitor generally referred to as a condenser, it is a two-terminal passive component
that will capable of storing energy in the form of electricity. These are the rechargeable
batteries mainly used in power supply. In the capacitors, electrical plates differ by a
dielectric medium and these are acts like a filter that allows only AC signals and blocks DC
Signals. The capacitors are classified into various types that are discussed below

Capacitors
Capacitor: A capacitor is used to store the energy in electrical form.
Polarized Capacitor: Stores electrical energy these must be a one way round.
Variable Capacitor: These capacitors are used to control the capacitance by adjusting
the Knob.
Trimmer Capacitor: These capacitors are used to control the capacitance by using
Screwdriver or similar tools.
Diodes
A Diode is an electronic component with two terminals that are anode and cathode. It
allows electron current flow from cathode to anode but it blocks another direction. The
diode will have low resistance in one direction and high resistance in another direction.
The diodes are classified into various types that are discussed below

Diodes
Diode: A diode allows the current flow in one direction.
Light Emitting Diode: It will emit the light when the electric current flows through it.
Zener Diode: It will allow a constant electric current after the breakdown voltage.
Photo Diode: Photodiode will convert light into respective current or voltage.

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Tunnel Diode: Tunnel diode is used for very high-speed operations.
Schottky Diode: Schottky diode is for forwarding low voltage drop.
Transistors
The transistors are invented in 1947 at Bell Laboratories to replace vacuum tubes, that it
will control the flow of current and voltage in the circuits. It is a three terminal device and
amplifies the current, transistors plays an important role in all modern electronics.

Transistors
NPN transistor: A P-type doped semiconductor material is placed in between two N-type
semiconductor materials. The terminals are the emitter, base, and collector.
PNP transistor: A N-type doped semiconductor material is placed in between two P-type
semiconductor materials. The terminals are an emitter, base, and collector.
Phototransistor: It is similar to bipolar transistors, but it converts light to current.
Field Effect Transistor: FET controls the conductivity with the help of an electric field.
N-channel JFET: The Junction Field Effect Transistors are simple of FET for switching.
P-channel JFET: P-type semiconductor is placed in between N-type junctions.
Enhancement MOSFET: Similar to DMOSFET but an absence of conducting channel.
Depletion MOSFET: The current flows from source to drain terminal.
Meters
A Meter is an instrument used for measuring voltage and current flow in electrical and
electronic components. These are used to measure the resistance and capacitance of the
electronic components.

Meters

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Voltmeter: It is used to measure voltage.
Ammeter: It is used to measure current.
Galvanometer: It is used to measure small currents.
Ohmmeter: It is used to measure the electrical resistance of a particular resistor.
Oscilloscope: It is used to measure voltage with respect to time for signals.

Switches
A Switch is an electrical/electronic component that will connect electrical circuits when the
switch is closed, otherwise, it will break an electrical circuit when the switch is open.

Switches
Push switch: It will pass the current flow when the switch is pressed.
Push to break switch: It will block the current flow when the switch is pressed.
Single pole single throw switch (SPST): Simply, it is an ON/OFF switch allows flow
only when the switch is in ON.
Single pole double throw switch (SPDT): In this type of switch current flows in two
directions.
Double pole single throw switch (DPST): It is a dual SPST switch, mainly used for
electrical lines.
Double pole double throw switch (DPDT): It is a dual SPDT switch.
Relay: A relay is a simple electromechanical switch made up of an electromagnet & a set
of contacts. These are found hidden in all sorts of devices.

Audio Devices
These devices convert an electric signal into sound signals and vice versa, which will be
audible to humans. These are input/output electronic components in the circuit diagram.

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Audio Devices
Microphone: converts sound or noise signal to an electrical signal.
Earphone: converts an electrical signal to a sound signal.
Loudspeaker: converts the electrical signal to sound signal but it will amplify version.
Piezo- transducer: converts flow of electrical energy to sound signal.
Bell converts the electrical signal to sound signal.
Buzzer: converts an electrical signal to sound signal.
Sensors
Sensors will sense or detect moving objects and devices, it will convert those signals into
electrical or optical. For example, a temperature sensor is used sense temperature
present in the room. The various types of sensors are

Sensors
Light-dependent resistor: These sensors will sense light.
Thermistor: These sensors will sense heat or temperature.
Logic Gates
Logic gates are the main building blocks in the digital circuits, logic gates will have two or
three inputs and a single output. The output produced by logic gates based on certain
logic. Basic Logic gate values represent in binary if we observe their truth tables.

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Logic Gates
AND Gate: The output value is HIGH when two inputs are HIGH.
OR Gate: The output value is HIGH when one of the inputs is HIGH.
NOT Gate: The output is the complement of the input.
NAND Gate: The complement of the AND gate is a NAND gate.
NOR Gate: The complement of the OR gate is a NAND gate.
X-OR Gate: The output is HIGH when an odd number of HIGH occurs in its inputs.
X-NOR Gate: The output is HIGH when an even number of HIGH occurs in its inputs.
Other Components
These are the some of the electronic/electrical components that are utilized in an
electronic circuit or electrical circuit design.

Other Components
Lighting Lamp: It is a bulb that will glow when certain current flows.
Indicator Lamp: It will convert electricity to light.
Inductor: It will generate a magnetic field when current flows through it.
Antenna: It is used to transmit and Receive the radio signals.

EXERCISE:
1. Define electronic component.
2. List different types of electronic components
3. Define passive component.
4. What are the characteristics of passive components?

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5. What are the characteristics of active components?
6. Define active component.
7. List different types of passive components
8. List different types of active components
9. Define resistor.
10. Define capacitor.
11. Define inductor.
12. Define diode.
13. Diode allows electric current when it is ________.
14. Diode blocks electric current when it is ________.
15. Define transistor.
16. Which types of materials are used to construct transistors?

REFERENCE:

1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.

2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.

3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.

4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.

5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.

DPP C2(b)

Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka

INFORMATION SHEET

PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 01
ELECTRONIC FUNDAMENTAL

WEEK 13

TOPIC 3.0 Automotive Electrical System
SUB-TOPIC 3.1. Electronic components

TOPIC After the lesson, student should be able to:
LEARNING 1. Identify electronic components, symbols and know its function.
OUTCOME 2. Manipulate electronic wiring diagram.
3. React with broken electronic components.
4. Assemble a simple electronic project.
5. Practice using digital and analog multimeter.
6. Practice using digital and analog oscilloscope.

4.1 Resistor
Resistor is basic component that is used in all the electronic circuits. It is a passive
element that resists the flow of electrons. Thus it allows only certain amount of current to
pass through it. Remaining current is converted into heat.
The working principle of bulb is that electricity is passed through the filament usually
tungsten, which is a resistor. The energy is converted to and released as light and heat.

Resistor Symbols

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Generally there are two standards that are used to denote the symbol of a resistor
viz.Institute of Electrical and Electronics Engineers (IEEE) and International Electro
Technical Commissions (IEC).
The IEEE symbol of resistor is a zigzag line as shown in the below figure.

Resistor IEEE Symbol

The IEC symbol

Resistor IEC Symbol

Why is a resistor used in a circuit?
Let us take an example to answer this question.
 Consider an LED connected to a battery of 9V. Assume the Forward current of the

LED is 3mA.
 If a resistor is connected between the Led and battery the Led will glow.
 If there is no resistor in between LED and battery, led will glow but after some time it

heats up enormously. This is because of the more current (>30 mA) Passing through
the LED.
 Thus Resistor is necessary to control the current flow.
 Resistor used in the circuit can be used for many purposes. For example, to adjust the
voltage levels, to provide biasing to active components, for dividing the voltage levels
etc.
 What is a resistor made out of?
 Resistors are made of ceramic rods coated with a metal or metal oxides.
 This coating determines the resistance value of the resistor.
 If coating is thicker, lower is the resistance value of the resistor.

What is a linear resistor?
Resistors that obey ohms’ law are called linear resistors. The resistance of these resistors
does not change with the varying current flowing through it.
Generally, resistors that obey ohm’s law are
1. Fixed resistors
2. Variable resistors

Fixed Resistors
 Fixed Resistors are those whose resistance value is fixed. Manufacturer sets a fixed

value to it.
 Ideally fixed resistors should work independent to changes in temperature, voltage

and frequency.
 This is not possible practically as all resistor materials have temperature coefficient

which leads to temperature dependency.
 The stray capacitance which is present in all resistors will result in impedance and

hence the actual resistance will be different from expected.
 Fixed resistors are available in different sizes, shapes, leaded, lead less, etc.

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 Some of the fixed resistors are
 Carbon Composition Resistor.
 Film resistors.
 Wire wound.

 Carbon Composition Resistors
 Carbon Composition Resistors are commonly used resistors.
 Because of their construction these resistors are manufactured at low cost.
 These resistors are composed of finely ground carbon along with ceramic clay
acting as a binding agent.
 The proportions of carbon and clay are the factor in determining the resistive
value. Resistance is higher when the quantity of carbon is lesser.

 They can be manufactured in wide range of values ranging from 1Ω to a high value as
22 MΩ.

 The advantage of carbon resistors is its ability to remain undamaged from high energy
pulses, available at very low cost and good durability.

 The disadvantages are high sensitivity to temperature, unstable noise properties and
stability issues when hot.

 They are easily affected by humidity and hence the tolerance is only 5%. They also
have a low-medium range power rating i.e. < 5W.

 Carbon composition resistors are suitable for high frequency applications as they have
low inductance.

Film Type Resistors
 Film type resistors are manufactured by a process called film deposition technique.
 Once the film is deposited on the insulating material, it is cut into a spiral helix pattern

with the help of a laser.
 The resistive value is controlled or maintained by controlling the thickness of the film

that is deposited.
 Two types of Film resistors are

a. Thin Film Resistors
b. Thick Film Resistors

Thin Film Resistors
 Thin film resistors are manufactured by depositing a resistive layer on an insulating

base like ceramic.
 The thickness of the resistive film is equal to or smaller than 0.1 micro meters.
 Vacuum deposition is the technique used to deposit the resistive film on the ceramic.
 The resistive material which is often an alloy of nickel and chromium called Nichrome

is sputtered on an insulator base which is ceramic.

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 This process will create a uniform film of 0.1 micrometer thick.
 The thickness of the metallic film can be controlled by controlling the time of

sputtering.
 Patterns are created by laser trimming process on the dense and uniform layer to

create and calibrate the resistive path and resistance value.
 Thin film resistors can be produced as SMD resistors or axial leaded resistors.
 Because of their high tolerance and low temperature coefficient, thin film resistors are

used in precision applications.
 Examples of thin Film resistors are

1. Metal Film,
2. Carbon Film and
 In metal films, nickel metal is used as resistive element and tin oxide in case of metal
oxide films.

 Metal Film type resistors have much higher tolerance and better temperature stability
when compared to carbon resistors.

 Hence they are used in applications like active filters where low temperature
coefficient and tight tolerance are required.

 Carbon film resistors are better than carbon composition resistors.
 Carbon film resistors are used in applications where the operating voltage and

temperature is high like laser and radar.

Thick Film Resistors
 In thick film resistors, the thickness of resistive film is nearly 1000 times thicker than

that in thin film resistors.
 The main difference between thick film and thin film resistors is the procedure for

applying the resistive film.
 The resistive film in thick film resistors is made from a mixture of a binder, carrier and

metal oxide.
 Glass frit bonding is used to bind the mixture. Carrier is the extract of organic solvent

and oxides of iridium or ruthenium are used.
 This mixture is made as a paste and the resistive film is produced by applying this paste

on to a ceramic base using stencil and screen printing process.
 Thick film resistors can be used in applications where less cost is important, high power

is handles and high stability is important.
 Example of Thick film resistor is

1. Metal Oxide Film.
 Metal oxide resistors have much better temperature stability and better surge current

capacity.

Wire Wound Type Resistors

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 Wire wound resistors are most precise and high power rated resistors.
 The construction of wire wound resistors involves a winding of thin metal or metal alloy

wire around an insulating substrate.
 Generally, the metals used are manganin or constantan and a nickel chromium alloy

which is also called as nichrome is used in case of metal alloy.
 The resistive value can be varied by varying wrap pattern, diameter, length and type of

alloy.

 The resistance tolerance of wire wound resistors is as tight as .005% and the power
ratings are in the range of 50W-300W.

 These are precision wire wound resistors. In case of power resistors, the tolerance is
5% and the power rating is in the range of kilo watts.

 They are limited to low frequency applications because of the nature of their
construction.

 Since there is a metal wire wound as a coil around an insulator, they act as inductors.
 This results in reactance and inductance and when used in A.C circuits there is a chance

of phase shift when operated at higher frequencies.
 There is a possibility to overcome this limitation by winding each half of wire in different

directions. This will cancel each other’s inductive effect.
 These resistors are called as Non-Inductive Wire Wound Resistors.
 Normally the cost of wire wound resistors is higher when compared to carbon

composition resistors.
 In high frequency applications Non-Inductive Wire Wound Resistors can be used but

their cost is more than normal wire wound resistors.
 Wire wound resistors are used in many applications. Some of them are circuit breakers,

transducers, temperature sensors and current sensors.

Variable Resistors
 Variable resistors are those in which the value of resistance can be varied or adjusted.
 The working of a variable resistor can be explained with the help of following diagram.

 The resistance path is provided by track and the terminals of device are connected to
track. Wiper is used to increase or decrease resistance through its motion.

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Potentiometer
 A potentiometer or pot is an electro mechanical resistor with three terminals and is the

most commonly used variable resistor.

 The two terminals on the either end will deliver a constant resistance which is the
formal resistance.

 The terminal in the centre is movable and is called Wiper. This movable wiper
maintains contact with the resistive surface.

 The resistance between first terminal and the wiper plus the resistance between wiper
and second terminal is equal to the formal resistance of the device.

 The name potentiometer is given to this device as it adjusts voltage using voltage
divider principle.

 While wiper is a rotating contact, some potentiometers have continuously adjustable
tapping points which are contacted with the third terminal called tappers and they also
act as continuously adjustable voltage divider.

 The best application is their use in tuning circuits an in radio receivers.

Preset
 Preset is a variable resistor which is used in occasional adjustment conditions.
 Generally, presets are mounted on printed circuit board and are adjusted using the

rotary control present on top of it with the help of a screw driver.
 In contrast to potentiometers where the resistance varies linearly, the resistance in

preset varies exponentially.
The symbol of a preset is as shown below.

Fig: Preset symbol
 Presets are made available in single turn and multi turn operations.
 Presets are used in designs where the value of the resistance is set in the circuit

during the time of production.
 Due to their sensitivity, presets are often used in sensing circuits like temperature or

light sensing.

Rheostat
 A rheostat is a two terminal variable resistor.
 In rheostat, one end of resistive track of a variable resistor and its wiper terminal are

connected to the circuit.
 This connection will limit the current in the circuit according to the position of the wiper.

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 Rheostats are used to control the resistance without interrupting the flow of current.
 Because of this significant flow of current, rheostats are made as wire wound

resistors.
 Rheostats are used in applications where current is more important than power rating.
 They are generally used in tuning circuits and power control applications.

Nonlinear Resistors
As the name indicates their resistance value varies with the varying Current flowing in the
resistor.Some nonlinear resistors are
 Varistor
 LDR
 Thermistor

Varistor
 It is an electronic component with non-linear current voltage characteristics.
 The resistance in varistor is changed according to the change in voltage across it.
 This makes it a voltage sensitive device hence it is also called Voltage Dependent

Resistor.

 The resistance of varistor is very high under normal operating conditions.
 But the resistance decreases dramatically when the voltage increases beyond the

rated value of varistor.
 Metal oxide Varistors are most common type of varistors.
 Grains of Zinc oxide are used because it provides P-N diode characteristics. Hence it

is used to protect electronic and electrical circuits from over voltage surges.
Light Dependent Resistor (LDR)
 Light Dependent Resistors or Photo resistors are light sensitive resistors whose

resistance varies according to the intensity of the light incident on them. The symbol of
Light dependent resistors is

Fig: LDR Symbol

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 Light dependent resistors are made of semiconductors with high resistance. In
absence of light or in dark, the resistance of light dependent resistors is very high
usually in the range of Mega Ohms (MΩ).

 In absence of light or in dark, the resistance of light dependent resistors is very high
usually in the range of Mega Ohms (MΩ).

 When light is incident on the surface of light dependent resistors, its resistance value
decreases.

 Thermistor
 Thermistor is a resistor whose resistance value varies with the temperature. It is a

type of transducer.
 These are mostly used for measuring the temperature. There are two types of

thermistors. NTC (Negative Temperature Coefficient), PTC (Positive temperature
Coefficient)
 As the temperature increases, resistance of the thermistor decreases for NTC
thermistor and for PTC Resistance increases with increase in temperature.
 They differ from temperature detectors. RTD are useful for large temperature ranges
where as these thermistors are useful from -90 to 1300

Other types
 Resistors can be further divided based on mounting, power rating.
 Resistors Types Based on Termination and Mounting

SMD Resistors
 Surface Mount Devices (SMD) are produced as a result of a technique called Surface-

mount Technology (SMT).
The development of Surface-Mount Technology and Surface Mount Devices is a result
of requirement of smaller, faster, cheaper and more efficient components by PCB
manufacturers.
 SMD resistors are smaller than their through-hole counterparts and are generally
rectangular but sometimes oval in shape.
 These rectangular chips have very small metal leads or metalized areas at either ends
which are used to make contact with the PCB and therefore eliminating the need for
holes on PCB and wire leads on resistors.
 A single SMD resistor is as shown in the figure.

 SMD resistors consist of an insulator substrate which is generally ceramic and a layer
of metal oxide film is deposited on this substrate.

 The value of resistance is determined by the thickness of the film.
 Because of their small size they are suitable for circuit boards.
 They have very little inductance and capacitance and can perform well at radio

frequencies.

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Through-hole Resistors
 Through-hole is a mounting technique where the components are inserted into holes

that are drilled on a PCB.
 For this purpose, the electronic component consists of small metallic leads.
 All the resistors with leads coming out of them for contact purpose come under

Through-hole resistors.
 Through-hole resistors are available in carbon composition resistors, carbon film

resistors, metal film resistors, metal oxide resistors, wire wound resistors and many
others.
 Apart from discrete components, through-hole resistors can be found as pack of
resistors with the usage of Dual in-line package and Single in-line package
techniques.

 These SIP and DIP resistors are generally used in resistor ladder networks, pull-up
and pull-down networks, bus terminators etc.

Network Resistors
 Network resistors are single package resistors with two or more resistors. They

generally come in Single in-line package or Dual in-line package.
 These SIP and DIP resistors are generally used in resistor ladder networks, pull-up

and pull-down networks, bus terminators etc.

 Resistor networks are used to reduce the board space, improve reliability, reduce
solder connections and improve tolerance matching.

 Generally, resistor networks are used in resistor ladders, bus terminators and small
computer system interface terminators.

 They are available as both surface mount devices and through-hole devices.

Resistor Color Codes
There are many different types of resistors available. In order to identify or calculate the
resistance value of a resistor, it is important to have a marking system. Resistor Color
Code is one way to represent the value of the resistance along with the tolerance.

Resistor color code is used to indicate the value of resistance. The standards for color
coding registers are defined in international standards IEC 60062. This standard
describes color coding for axially leaded resistors and numeric code for SMD resistors.

There are several bands to specify the value of resistance. They even specify tolerance,
reliability and failure rate. The number of bands vary from three to six. In case of 3 band
code, the first two indicate the value of resistance and the third band acts as multiplier.

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Three Band Resistor Color Code
 The three band color code is very rarely used.
 The first band from the left indicates the first significant figure of the resistance.
 The second band indicates the second significant number.
 The third band indicates the multiplier.
 The tolerance for three band resistors is generally 20%.
 The color code table corresponding to three band resistors is shown below.

For example, if the colors on the resistor are in the order of Yellow, Violet and Red from
left, then the resistance can be calculated as
47× 102± 20 %. This is 4.7 KΩ± 20%.
This means the resistance value lies in the region of 3760Ω to 5640Ω.
Four Band ResistorColor Code
 Four band color code is the most common representation in resistors.
 The first two bands from the left are used to indicate the first and second significant

digits of resistance.
 The third band is used to indicate the multiplier.
 The fourth band is used to indicate tolerance.
 There is a significant gap between third and fourth bands. This gap helps in resolving

the reading direction. The color code table for four band resistors is as shown below.

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For example, if the colors on a four band resistor are in the order Green, Black, Red and
Yellow then the value of resistance is calculated as 50 * 104± 2 % = 500KΩ± 2%.
tolerance Letter Coding for Resistors
The letter code for tolerance is shown below
 B = 0.1%
 C = 0.25 %
 D = 0.5 %
 F=1%
 G=2%
 J=5%
 K = 10 %
 M = 20 %
K and M should not be confused with kilo and mega Ohms.
4.2 Capacitor
Capacitor is also known as condenser. This is one of the passive components like
resistor. Capacitor is generally used to store the charge. In capacitor the charge is stored
in the form of “electrical field”. Capacitors play a major role in many electrical and
electronic circuits.

Generally, a capacitor has two parallel metal plates which are not connected to each other.
The two plates in the capacitor are separated by non-conducting medium (insulating
medium) this medium is commonly known as Dielectric.

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There are different types and different shapes of capacitors available, from very small
capacitors which are used in resonance circuits to large capacitors for stabilising HVDC
lines. But all capacitors are doing the same work that is storing the electrical charge.
The shape of a capacitor is rectangular, square, circular, cylindrical or spherical shape.
Unlike a resistor, an ideal capacitor does not dissipate energy. As the different types of
capacitors are available different symbols were available to represent them which are
shown below.

Why capacitors are important?
Capacitors have many properties like
1. They can store the energy and it can dissipate this energy to the circuit when ever

required.
2. They can block DC and allow AC to flow through it, and this can couple one part of the

circuit with the other.
3. Circuits with capacitors depend on the frequency, so can be used to amplify certain

frequencies.
4. As the capacitors when applied with AC input , the current leads the voltage and thus

in power applications it increases the pay load power and makes it more economical.
5. It allows high frequencies and so it can be used as a filters either to filter low

frequencies or to collect high frequencies.
6. As the reactance and frequency of the capacitor are inversely related, this can be

used to increase or decrease the circuit impedance at certain frequency and can be
used as filter.
Likewise, capacitors exhibit many properties, when used in AC or DC circuits and hence
they play important role in electrical and electronic circuits.

Construction of a Capacitor
As said before, there are different types of capacitors. These different types will have
different type of construction. A Parallel plate capacitor is the simplest capacitor. Let us
understand the construction of this capacitor.
It consists of two metal plate separated by a distance. The space between these two plates
is filled with a dielectric material. The two leads of the capacitor are taken from these two
plates.
The capacitance of the capacitor depends on the distance between the plates and area of
the plates. Capacitance value can be changed by varying any of these parameters.
A variable capacitor can be constructed by making one of these plates fixed and other
moving.

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Dielectric of a Capacitor
Dielectric acts as an insulating material between the plates. Dielectric can be any non-
conducting material such as ceramic, waxed paper, mica, plastic or some form of a liquid
gel.
Dielectric also plays an important in deciding the value of capacitance. As the dielectric is
introduced between the plates of the capacitor, its value increases.
Different dielectric materials will have different dielectric constants; however, this value is
>1.
Below table gives value of dielectric constant for each dielectric material

Dielectric can be of two types
1. Polar dielectrics: These dielectrics will have permanent dielectric movement
2. Non Polar dielectrics: These will have temporary dielectric moment. By placing
them in a electric field they can be induced with dipole moments.

Complex Permittivity
The product of the relative permittivity (εr) of the dielectric material and permittivity of free
space (εo) is known as “Complex permittivity” or “Actual permittivity” of the dielectric
material. The expression for the complex permittivity is given as follows,

ε = ε0 * εr
The value of complex permittivity will always be equal to the relative permittivity, because
the permittivity of free space is equal to ‘one’. The value of dielectric constant or complex
permittivity varies from one dielectric material to another.
Some standard values of complex permittivity (ε) for common dielectric materials are Air =
1.0005, Pure Vacuum = 1.0000, Mica = 5 to 7, Paper = 2.5 to 3.5, Wood = 3 to 8, Glass =
3 to 10 and Metal Oxide Powders = 6 to 20 and etc.
capacitors can be classified according to the properties and characteristics of their
insulating or dielectric material, they are given below as
1. High Stability & Low Loss Capacitors — Mica, Low-K Ceramic, and Polystyrene

capacitors are examples for this type.
2. Medium Stability & Medium Loss Capacitors – Paper, Plastic Film, and High-K

Ceramic capacitors are examples for this type.
3. Polarized Capacitors – Example for this type of capacitors are Electrolytic, Tantalum’s.

Working
As said before capacitor consists of two conductor separated by a dielectric, when there is
any potential difference between the two conductor’s electric potential is developed. This
causes the capacitor to charge and discharge.

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Let us understand this in a practical way. When the capacitor is connected to a battery (a
DC source) , current starts flowing through the circuit .
Thus negative charge is accumulated on one plate and positive charge is accumulated on
the other plate. This process continuous until the capacitor voltage reaches supply
voltage.
When the charging voltage is equal to the supply voltage capacitor stops charging further
even though the battery is connected. When the battery is removed two plates will be
accumulated with positive and negative charges. Thus the charge is stored in the
capacitor.
But when the supply voltage is from an AC source it charges and discharges
continuously. The rate of charging and discharging depends on the frequency of the
source.

Example
Working can be understood using simple example here. Below circuit shows two switches
A and B. When switch 1 is closed, current starts flowing from from the battery to the
capacitor. When the capacitor voltage reaches the supply voltage ,it stops charging
further.

Now connect the switch to position B. Now you can observe the LED starts glowing and
this slowly fades out as the capacitor is discharging.

Capacitance of the capacitor is given by
C=KεA/d
or
C= εA/4πd
or

C = εo * εr (A/d)
Where,
C – Capacitance of the capacitor
A – Area between the plates
D – Distance between the two Plates

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εo – Permittivity of free space
εr – Relative permittivity.
K- Dielectric Constant

Capacitance of a Capacitor
Capacitance is the property of the capacitor that defines the maximum amount of electrical
charge stored in it.it exists in nature everywhere.
Capacitance may vary depending on the shape of the capacitor. Capacitance can be
calculated by using the geometry of the conductors and dielectric material properties. Let
us see the capacitance of a parallel plate capacitor.
Capacitance is defined as the ratio of charge (Q) on the either plates to the potential
difference(V) between them,

C =Q/V,
Thus current can be obtained as

I(t)=C[d(v)/d(t)]
This can be expressed Farads (F) which is named after English physicist Michael
Faraday.
From the above definition we can observe that capacitance is directly proportional to the
charge (Q) and is inversely proportional to the voltage (V).
Capacitance of the capacitor can be increased by increasing the number of plates, which
helps to maintain the same size of the capacitor. Here, area of the plates is increased.
Standard units of capacitance
Generally, Farads is a high value so, capacitance is expressed as sub units of capacitor
real time such as as micro farads(uF), nano farads(nF) and pico farads(PF).
Most of the electrical and electronic applications are covered by the following standard
unit (SI) prefixes for easy calculations,

 1 mF (milli farad) = 10−3 F = 1000 μF = 1000000 nF
 1 μF (microfarad) =10−6 F = 1000 nF = 1000000 pF
 1 nF (nano farad) = 10−9 F = 1000 pF
 1 pF (picofarad) = 10−12 F
To convert µF to nF or pF or to a wide range of other units and vice versa, we need to
use the Electric Capacitance Unit Converter.

Voltage Rating of a Capacitor
This is not voltage until which the capacitor charges but the maximum voltage until which
the capacitor can operate safely. This voltage is called as working voltage (WV) or DC
working voltage (DC-WV). Below figure shows the voltage rating of the capacitor.

If the capacitor is applied with voltage greater than this voltage, it may be damaged by
producing an arc between the plates due to dielectric break down.
While designing the circuits with capacitors, care should be taken such that the voltage
rating of the capacitor is greater than the voltage used in the circuit. For example, if the

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circuit operating voltage is 12V then it is necessary to choose a capacitor with voltage
rating of 12V or above.
This working voltage of a capacitor depends on the factors like dielectric material used
between the capacitor plates, dielectric thickness and also on the type of circuit which is
used.

Types of Capacitors

Each capacitor type has its own advantages and disadvantages. The characteristics and
areas of applications may vary from one capacitor to other. Hence, when choosing a
capacitor, following few of many factors must be considered.
 Size: Both the physical dimension and the value of the capacitance is important.
 Working Voltage: It is an important characteristic of the capacitor. It specifies the

maximum voltage that can be applied across the capacitor.
 Leakage Current: A small amount of current will flow through dielectric as they are not

the perfect insulators. This is called leakage current.
 Equivalent series resistance: The terminals of the capacitor have a small amount of

resistance (usually less than 0.1Ω). This resistance becomes a problem when the
capacitor used at high frequencies.
These factors determine how and in what applications a particular type of capacitor can be
used. For example, the rated voltage of an electrolytic capacitor is larger when compared
to a ceramic capacitor in the similar capacitance range.
So they are generally used in power supply circuits. Similarly, some capacitors have very
low leakage current and others have very high leakage current. Depending on the
application, appropriate capacitor should be chosen.

Dielectrics in Capacitors
Fixed capacitors are more common types of capacitors. It is difficult to find an electronic
circuit without a capacitor. Most of the capacitors are named after the dielectric used in
the construction. Some of the common dielectrics used in the construction of capacitors
are:

 Ceramic
 Paper
 Plastic film
 Mica
 Glass
 Aluminium Oxide
 Tantalum Pentoxide

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 Niobium Pentoxide
The last three are used in electrolytic capacitors. Despite the use of different kinds of
dielectrics in the construction of capacitors, the functionality of the capacitor doesn’t
change: to store energy in the form of electric charge between the parallel plates.

Capacitors in series
How to connect capacitors in Series?
Capacitors in series means two or more capacitors connected in a single line. Positive
plate of the one capacitor is connected to the negative plate of the next capacitor.

Here,
QT =Q1 = Q2 = Q3 = ———= Q
IC = I1 = I2 = I3 = ——— = IN

When the capacitors are connected in series Charge and current is same on all the
capacitors.
Why is the charge of capacitors in series the same?
For series capacitors same quantity of electrons will flow through each capacitor because
the charge on each plate is coming from the adjacent plate. So, coulomb charge is same.
As current is nothing but flow of electrons, current is also same.
What is the equivalent capacitance?
Equivalent capacitance is the overall capacitance of the capacitors. Let us see how to
calculate the capacitance when they are in series.
Below is the figure showing three capacitors connected in series to the battery. When the
capacitors are connected in series the adjacent plates get charged due to electrostatic
induction.

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Each plate will have different potential. But the magnitude of charge on the plates is

same.

First plate of the C1 will have potential V1 which is equal to the voltage of the battery and

second plate will have potential less than V1. Let it be V2.

Now the first plate of C2 will have potential equal to V2 and second plate will have

potential less than V3 let it be V4.

First plate of C3 will have potential V5 (V5=V4) and the potential of second plate is less

than V5. Let it be V6.

But the overall potential difference between the plates is equal to the emf of the battery.

So VT = V1+V2+V3

But we know that, Q=CV

C=Q/V

Ceq = Q/V1 + Q/V2 + Q/V3 (As charge is same)

1/Ceq = (V1+ V2+ V3)/Q

VT = Q/Ceq = Q/C1 + Q/C2 + Q/C3

Hence,1/Ceq = 1/C1 + 1/C2 + 1/C3

If N capacitors are connected in series, then equivalent capacitance can be given as

below.

1/Ceq = 1/C1 + 1/C2 +……… + 1/CN

Thus when the capacitors are in series connection, the reciprocal of the equivalent

capacitance is equal to the sum of the reciprocals of the individual capacitance of the

capacitors in the circuit.

Capacitors in Series Example
Calculate the equivalent capacitance and the individual voltage drops across the set of two
capacitors in series have 0.1uF and 0.2uF respectively when connected to a 12V a.c.
supply.
Equivalent capacitance,

1/Ceq = 1/C1 + 1/C2
Ceq = (C1C2) / (C1 + C2)
Ceq = (0.1uF*0.2uF) / (0.1uF+0.2uF)

Ceq = 0.066uF = 66nF
Voltage drops across the two given capacitors in series are,

V1 = (C2*VT)/ (C1+C2) = (0.2uF*12V)/ (0.1uF+0.2uF) = 8Volts
V2 = (C1*VT)/ (C1+C2) = (0.1uF*12V)/ (0.1uF+0.2uF) = 4Volts

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From these results we observed that the equivalent capacitance 66nF is less than the
smallest capacitance 0.1uF of the given two capacitors. The individual voltage drops
across the given two capacitors are different.
But the sum of individual voltage drops of both the capacitors is equal to the total voltage.
i.e 8V+4V=12V.
Now we calculate the charge stored in individual capacitor,
Q1 = V1* C1 = 8V * 0.1uF = 0.8uC
Q2 = V2* C2 = 4V * 0.2uF = 0.8uC
Here we observed that equal charge 0.8uC is stored in both the capacitors C1 and C2
which are connected in series.

Capacitors in Series Summary
• Charge on the capacitors is same in series connection.
• Equivalent capacitance of the capacitors is less than the smallest capacitance in series.
• Equivalent capacitance of n capacitors in series is given as

1/Ceq = 1/C1 + 1/C2 +……… + 1/CN

Capacitors in Parallel Circuits

Why do we connect capacitors in parallel?
There is an advantage of connecting capacitors in parallel than in series. When the
capacitors are connected in parallel the total capacitance value is increased. There are
some applications where higher capacitance values are required.

How to connect capacitors in Parallel?
Below figure shows the connection of capacitors in parallel. All the positive terminals are
connected to one point and negative terminals are connected to another point.

What is Equivalent capacitance of the capacitors in parallel?
 All the capacitors which are connected in parallel have the same voltage and is equal

to the VT applied between the input and output terminals of the circuit.
 Then, parallel capacitors have a ‘common voltage’ supply across them.i.e. VT = V1 =

V2 etc.
 The equivalent capacitance, Ceq of the circuit where the capacitors are connected in

parallel is equal to the sum of all the individual capacitance of the capacitors added
together.
 This is because the top plate of each capacitor in the circuit is connected to the top
plate of adjacent capacitors. In the same way the bottom plate of each capacitor in the
circuit is connected to the bottom plate of adjacent capacitors.

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Let us see how to calculate the equivalent capacitance of capacitors when connected in
parallel. Consider two capacitors connected as shown in the below circuit.

The total charge (Q) across the circuit is divided between the two capacitors, means the
charge Q distributes itself between the capacitors connected in parallel. charge Q is equal
to the sum of all the individual capacitor charges.
Thus Q=Q1+Q2
Where Q1, Q2 are charges at capacitors C1 and C2.
We know that,

Q=Ceq VT
Here, Q = Q1+Q2
Ceq VT = C1xV1+C2xV2
Since VT = V1 = V2 = V
Ceq VT = C1xV+C2xV
Ceq VT = (C1+C2) V
Hence Ceq=C1+c2
If N capacitors are connected in parallel, then Ceq=C1+C2+C3+——Cn
Thus equivalent capacitance of the capacitors which are connected in parallel is equal to
the sum of the individual capacitance of the capacitors in the circuit.

Capacitors in Parallel Example No1
Consider the capacitance values of the two capacitors C1 =0.2uF and C2 =0.3uF which
are shown in above figure 4. Now calculate the equivalent capacitance of the circuit.
We know that the Equivalent capacitance,
Ceq = C1 + C2
Ceq =0.2uF + 0.3uF
Ceq =0.5uF
One important point to remember about parallel connected capacitor circuits, the
equivalent capacitance (Ceq) of any two or more capacitors connected together in parallel
will always be greater than the value of the largest capacitor in the circuit as we are
adding together values. So in our example above Ceq =0.5uF whereas the largest value
capacitor in the circuit is only 0.3uF.

When capacitors are connected in parallel?
Here are some applications where capacitors are connected in parallel.
 In some DC supplies for better filtering small capacitors with superior ripple factor are

used. These are connected in parallel to increase the capacitance value.

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 This can be used in automotive industries in large vehicles like trams for regenerative
braking. These application may require large capacitance values than the capacitance
usually available in the market.

Capacitors in parallel Summary
 Voltage on the capacitors is same when connected in parallel. The equivalent voltage

of the parallel capacitors is equal to the smallest voltage rating capacitor in parallel.
 The overall capacitance value of the capacitors is sum of all the capacitance values

connected in parallel.
 Equivalent capacitance of n capacitors in parallel is Ceq=C1+C2+C3…Cn.

4.3 Semiconductor

Semiconductors have the electrical properties in between insulators and conductors.
Smart examples of perfect semiconductors are silicon (Si), germanium (Ge) and gallium
arsenide (GaAs). These elements have only a few electrons within the parental atomic
structure that form a crystal lattice. Silicon, the foremost basic semiconductor material
contains four valence electrons within the outer shell forming four strong covalent bonds
with four adjacent silicon atoms, such that each atom shares an electron with the
neighbouring atom creating a strong covalent bond. The silicon atoms are organized in a
lattice form, creating them a crystalline structure.
Conducting electric current is feasible with silicon semiconductor crystal by supplying
external potential to the semiconductor and incorporating the impurity dopants into the
semiconductor crystal thereby creating positive and negative charged holes.

Pure Silicon Atom Structure:

The silicon atom has 14 electrons; however, the orbital arrangement has solely 4 valence
electrons to be shared by alternative atoms. These valence electrons play a crucial role in
photo voltaic effect. Large number of silicon atoms bond together to make a crystalline
structure. In this structure, each silicon atom shares one of its four valence electrons with
their neighbouring silicon atoms. The solid silicon crystal composed of a regular series of
units of five silicon atoms. This regular and fixed arrangement of silicon atoms are unit is
referred to as a crystal lattice.

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N-Type Semiconductor:
Impurities like phosphorous, arsenic and antimony are added to the silicon crystalline
structure, to transform intrinsic semiconductor into extrinsic semiconductor. These
impurity atoms are known as pentavalent impurities as a result of the five valence
electrons in the outermost shell to share the free electrons with the neighbouring atoms.
Pentavalent impurity atoms are also known as donors because the five valence electrons
in the impurity atom bond with the four valence electrons of silicon forming four covalent
bonds, leaving one free electron. Each impurity atom produces a free electron within the
conduction band. Once a positive potential is applied to the N-type semiconductor, the
remaining free electrons form a drift to produce an electrical current.

An N-type semiconductor is a better conductor than the intrinsic semiconductor material.
The majority charge carriers in N-type semiconductors are electrons and minority charge
carriers are holes. The N-type semiconductors are not negatively charged, because the
negative charge of donor impurity atoms is balanced by the positive charge within the
nucleus.
The major contribution to the electric current flow is negatively charged electrons though
there is some amount of contribution by the positively charged holes due to electron-hole
pair.
N-type Semiconductor Doping:
If group 5 element, such as Antimony impurity is added to the silicon crystal, the
Antimony atom builds four covalent bonds with four silicon atoms by bonding the valence
electrons of antimony with the valence electrons within the silicon outermost shell, leaving
one free electron. Therefore the impurity atom has donated a free electron to the
structure so these impurities are referred to as donor atoms.

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P-Type Semiconductor:
The group 3 elements such as boron, aluminium and indium are supplementary to the
silicon crystalline structure having solely three electrons within the outermost shell, form
three closed covalent bonds, leaving the hole in the covalent bond structure and therefore
a hole in the valence band of the energy level diagram. This action leaves an abundant
number of positively charged carriers referred to as holes in the crystalline structure when
there is electron deficiency. These group 3 elements are called as trivalent impurity
atoms.
The presence of abundant holes attracts the neighbouring electrons to sit in it. As long as
the electron fills the holes in the silicon crystal there will be new holes behind the electron
as it goes far from it. The newly created holes successfully attract the electrons, creating
other new holes leads to the movement of holes, creating a standard electric current flow
in the semiconductor.

The movement of holes in the silicon crystal seems the silicon crystal as a positive pole.
As long as the impurity atoms invariably generate holes, group 3 elements are referred to
as acceptors as a result of the impurity atoms are continually accepting the free electrons.
The doping of group 3 elements in silicon crystal leads to P-type semiconductor. In this P-
type semiconductor holes are the majority charge carriers and electrons are the minority
charge carriers.
P-Type Semiconductor Doping:

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If group 3 elements such as such as boron, gallium and indium are added to the
semiconductor crystal, the impurity atoms having three valence electrons form three
strong covalent bonds with the silicon crystal valence electrons leaving one vacancy. This
vacancy is called as a hole and it is diagrammatically represented by a small circle or
positive sign due to the absence of a negative charge.

Semiconductor Basics Summary:
N-type materials are type of materials formed by adding group 5 elements (pentavalent
impurity atoms) to the semiconductor crystals and conduct the electric current by
movement of electrons.

In N-type Semiconductors:
 The impurity atoms are pentavalent elements.
 Impurity elements with solid crystal give a large number of free electrons.
 Pentavalent impurities are also called as donors.
 Doping gives the less number of holes in relation to the number of free electrons.
 Doping with group 5 elements results in positively charged donors and negatively
charged free electrons.

P-type materials are a type of materials formed when group 3 elements (trivalent impurity
atoms) are added to the solid crystal. In these semiconductors the current flow is mainly
due to the holes.

In P-type Semiconductors:
1. The impurity atoms are trivalent elements.
2. Trivalent elements results in excess number of holes which always accepts
electrons. Hence trivalent impurities are called as acceptors.
3. Doping gives the less number of free electrons in relation to the number of holes.
4. Doping results in negatively charged acceptors and positively charged holes

Both p-type and N-type are electrically neural on their own because the contribution of
electrons and holes required for conducting electrical current are equal due to electron-
hole pair. Both boron (B) and antimony (Sb) are called metalloids because they are the
most commonly used doping agents for the intrinsic semiconductor to improve the
properties of conductivity.

4.4 Diode
Diodes are electronic components functions as a one-way valve it means it allow current
to flow in one direction. These diodes are manufactured by the semiconductor materials

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germanium, silicon and selenium. Operation of diode can be classified in two ways, if it
allows the current then it is forward biased otherwise it is reverse biased.
For silicon diodes the forward voltage is 0.7v and for germanium it is 0.3v. In silicon diode
the dark band indicates the cathode terminal and the other terminal is anode. Generally,
diodes are used as reverse polarity protector and transient protector. There are many types
of diodes and some of these are listed as follows.

1. Small Signal Diode
It is a small device with disproportional characteristics and whose applications are mainly
involved at high frequency and very low currents devices such as radios and televisions
etc. To protect the diode from contamination it is enveloped with a glass so it is also named
as Glass Passivated Diode which is extensively used as 1N4148.
The appearance of signal diode is very small when compared with the power diode. To
indicate the cathode terminal one edge is marked with black or red in color. For the
applications at high frequencies the performance of the small signal diode is very effective.
With respect to the functional frequencies of the signal diode the carrying capacity of the
current and power are very low which are maximum nearly at 150mA and 500mW.
The signal diode is a silicon doped semiconductor diode or a germanium doped diode but
depending up on the doping material the characteristics of the diode varies. In signal diode
the characteristics of the silicon doped diode is approximately opposite to the germanium
doped diode.
The silicon signal diode has high voltage drop at the coupling about 0.6 to 0.7 volts so, it
has very high resistance but low forward resistance. On other hand germanium signal diode
has low resistance due to low voltage drop nearly at 0.2 to 0.3 volts and high forward
resistance. Due to small signal the functional point is not disrupted in small signal diode.

2. Large Signal Diode
These diodes have large PN junction layer. Thus the transformation of AC to DC voltages
is unbounded. This also increases the current forward capacity and reverse blocking
voltage. These large signals will disrupt the functional point also. Due to this it is not suitable
for high frequency applications.
The main applications of these diodes are in battery charging devices like inverters. In
these diodes the range of forward resistance is in Ohms and the reverse blocking
resistance is in mega Ohms. Since it has high current and voltage performance these can
be used in electrical devices which are used to suppress high peak voltages.

3. Zener Diode
It is a passive element works under the principle of zener breakdown. First produced by
Clarence zener in 1934.It is similar to normal diode in forward direction, it also allows
current in reverse direction when the applied voltage reaches the breakdown voltage. It is
designed to prevent the other semiconductor devices from momentary voltage pulses. It
acts as voltage regulator.

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4. Light Emitting Diode (LED)
These diodes convert the electrical energy in to light energy. First production started in
1968. It undergoes electroluminescence process in which holes and electrons are
recombined to produce energy in the form of light in forward bias condition.
Earlier they used in inductor lamps but now in recent applications they are using in
environmental and task handling. Mostly used in applications like aviation lighting, traffic
signals, camera flashes.

5. Constant Current Diodes
It is also known as current-regulating diode or constant current diode or current-limiting
diode or diode-connected transistor. The function of the diode is regulating the voltage at
a particular current.
It functions as a two terminal current limiter. In this JFET acts as current limiter to achieve
high output impedance. The constant current diode symbol is shown below.

6. Schottky Diode
In this type of diode, the junction is formed by contacting the semiconductor material with
metal. Due to this the forward voltage drop is decreased to min. The semiconductor material
is N-type silicon which acts as an anode and the metal acts as a cathode whose materials
are chromium, platinum, tungsten etc.
Due to the metal junction these diodes have high current conducting capability thus the
switching time reduces. So, Schottky has greater use in switching applications. Mainly
because of the metal- semiconductor junction the voltage drop is low which in turn increase
the diode performance and reduces power loss. So, these are used in high frequency
rectifier applications. The symbol of Schottky diode is as shown below.

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7. Shockley Diode
It was the invention of first semiconductor devices it has four layers. It is also called as
PNPN diode. It is equal to a thyristor without a gate terminal which means the gate terminal
is disconnected. As there is no trigger inputs the only way the diode can conduct is by
providing forward voltage.
It stays on one’s it turned “ON” and stays off one’s it turned “OFF”. The diode has two
operating states conducting and non-conducting. In non-conducting state the diode
conducts with less voltage.

The symbol of the Shockley diode is as follows:

Shockley Diode Applications
 Trigger switches for SCR.
 Acts as relaxation oscillator.

8. Step Recovery Diodes
It is also called as snap-off diode or charge-storage diode. These are the special type of
diodes which stores the charge from positive pulse and uses in the negative pulse of the
sinusoidal signals. The rise time of the current pulse is equal to the snap time. Due to this
phenomenon it has speed recovery pulses.
The applications of these diodes are in higher order multipliers and in pulse shaper circuits.
The cut-off frequency of these diodes is very high which are nearly at Giga hertz order.
As multiplier this diode has the cut-off frequency range of 200 to 300 GHz. In the operations
which are performing at 10 GHz range these diodes plays a vital role. The efficiency is high
for lower order multipliers. The symbol for this diode is as shown below.

9. Tunnel Diode
It is used as high speed switch, of order nano-seconds. Due to tunnelling effect it has very
fast operation in microwave frequency region. It is a two terminal device in which
concentration of dopants is too high.
The transient response is being limited by junction capacitance plus stray wiring
capacitance. Mostly used in microwave oscillators and amplifiers. It acts as most negative

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conductance device. Tunnel diodes can be tuned in both mechanically and electrically. The
symbol of tunnel diode is as shown below.

Tunnel Diode Applications
1. Oscillatory circuits.
2. Microwave circuits.
3. Resistant to nuclear radiation.

10. Varactor Diode
These are also known as Varicap diodes. It acts like the variable capacitor. Operations are
performed mainly at reverse bias state only. These diodes are very famous due to its
capability of changing the capacitance ranges within the circuit in the presence of constant
voltage flow.
They can able to vary capacitance up to high values. In varactor diode by changing the
reverse bias voltage we can decrease or increase the depletion layer. These diodes have
many applications as voltage controlled oscillator for cell phones, satellite pre-filters etc.
The symbol of varactor diode is given below.

Varactor Diode Applications
1. Voltage-controlled capacitors.
2. Voltage-controlled oscillators.
3. Parametric amplifiers.
4. Frequency multipliers.
5. FM transmitters and Phase locked loops in radio, television sets and cellular
telephone.

11. Laser Diode
Similar to LED in which active region is formed by p-n junction. Electrically laser diode is
p-i-n diode in which the active region is in intrinsic region. Used in fibre optic
communications, barcode readers, laser pointers, CD/DVD/Blu-ray reading and
recording, Laser printing.

Laser Diode Types:
 Double Heterostructure Laser: Free electrons and holes available simultaneously
in the region.
 Quantum Well Lasers: lasers having more than one quantum well are called multi
quantum well lasers.
 Quantum Cascade Lasers: These are heterojunction lasers which enables laser
action at relatively long wavelengths.
 Separate Confinement Heterostructure Lasers: To compensate the thin layer
problem in quantum lasers we go for separate confinement heterostructure lasers.
 Distributed Bragg Reflector Lasers: It can be edge emitting lasers or VCSELS.

The symbol of the Laser Diode is as shown:

DPP C2(b)

12. Transient Voltage Suppression Diode
In semiconductor devices due to the sudden change in the state voltage transients will
occur. They will damage the device output response. To overcome this problem voltage
suppression diode diode are used. The operation of voltage suppression diode is similar to
Zener diode operation.
The operation of these diodes is normal as p-n junction diodes but at the time of transient
voltage its operation changes. In normal condition the impedance of the diode is
high. When any transient voltage occurs in the circuit the diode enters in to the avalanche
breakdown region in which the low impedance is provided.
It is spontaneously very fast because the avalanche breakdown duration ranges in Pico
seconds. Transient voltage suppression diode will clamp the voltage to the fixed levels,
mostly its clamping voltage is in minimum range.
These are having applications in the telecommunication fields, medical, microprocessors
and signal processing. It responds to over voltages faster than varistors or gas discharge
tubes.
The symbol for Transient voltage suppression diode is as shown below.

The diode is characterized by
 Leakage current
 Maximum reverse stand-off voltage
 Breakdown voltage
 Clamping voltage
 Parasitic capacitience
 Parasitic inductance
 Amount of energy it can absorb

13. Gold Doped Diodes
In these diodes gold is used as a dopant. These diodes are faster than other diodes. In
these diodes the leakage current in reverse bias condition also less. Even at the higher
voltage drop it allows the diode to operate in signal frequencies. In these diodes gold helps
for the faster recombination of minority carriers.

14. Super Barrier Diodes
It is a rectifier diode having low forward voltage drop as schottky diode with surge handling
capability and low reverse leakage current as p-n junction diode. It was designed for high
power, fast switching and low-loss applications. Super barrier rectifiers are the next
generation rectifiers with low forward voltage than schottky diode.

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15. Peltier Diode
In this type of diode, at the two material junction of a semiconductor it generates a heat
which flows from one terminal to another terminal. This flow is done in only single direction
that is as equal to the direction of current flow.
This heat is produced due to electric charge produced by the recombination of minority
charge carriers. This is mainly used in cooling and heating applications. This type of diodes
used as sensor and heat engine for thermo electric cooling.

16. Crystal Diode
This is also known as Cat’s whisker which is a type of point contact diode. Its operation
depends on the pressure of contact between semiconductor crystal and point.
In this a metal wire is present which is pressed against the semiconductor crystal. In this
the semiconductor crystal acts as cathode and metal wire acts as anode. These diodes are
obsolete in nature. Mainly used in microwave receivers and detectors.
Crystal Diode Applications

 Crystal diode rectifier
 Crystal diode detector
 Crystal radio receiver

17. Avalanche Diode
This is passive element works under principle of avalanche breakdown. It works in
reverse bias condition. It results large currents due to the ionisation produced by p-n
junction during reverse bias condition.
These diodes are specially designed to undergo breakdown at specific reverse voltage to
prevent the damage. The symbol of the avalanche diode is as shown below:

Avalanche Diode Uses
 RF Noise Generation: It acts as source of RF for antenna analyser bridges and also
as white noise generators. Used in radio equipment and also in hardware random
number generators.
 Microwave Frequency Generation: In this the diode acts as negative resistance
device.
 Single Photon Avalanche Detector: These are high gain photon detectors used in
light level applications.

18. Silicon Controlled Rectifier
It consists of three terminals they are anode, cathode and a gate. It is nearly equal to the
Shockley diode. As its name indicates it is mainly used for the control purpose when small
voltages are applied in the circuit. The symbol of the Silicon Controlled Rectifier is as shown
below:

DPP C2(b)

Modes of Operation:
 Forward blocking mode (off state): In this j1 and j3 forward biased and j2 is reverse
biased. It offers high resistance below break over voltage and hence it is said to be
off state.
 Forward conduction mode (on state): By increasing the voltage at anode and
cathode or by applying positive pulse at the gate we can turn ON. To turn off the
only way is to decrease the current flowing through it.
 Reverse blocking mode (off state): SCR blocking the reverse voltage is named as
asymmetrical SCR. Mostly used in current source inverters.

19. Vacuum Diodes
Vacuum diodes consist of two electrodes which will acts as an anode and the cathode.
Cathode is made up of tungsten which emits the electrons in the direction of anode. Always
electron flow will be from cathode to anode only. So, it acts like a switch.
If the cathode is coated with oxide material, then the electrons emission capability is high.
Anode is a bit long in size and in some cases their surface is rough to reduce the
temperatures developing in the diode. The diode will conduct in only one case that is when
the anode is positive regarding to cathode terminal. The symbol is as shown in figure:

20. PIN Diode
The improved version of the normal P-N junction diode gives the PIN diode. In PIN diode
doping is not necessary. The intrinsic material means the material which has no charge
carriers is inserted between the P and N regions which increase the area of depletion layer.
When we apply forward bias voltage the holes and electrons will pushed into the intrinsic
layer. At some point due to this high injection level the electric field will conduct through the
intrinsic material also. This field made the carriers to flow from two regions. The symbol of
PIN diode is as shown below:

PIN Diode Applications:
 Rf Switches: Pin diode is used for both signal and component selection. For
example, pin diodes act as range-switch inductors in low phase noise oscillators.
 Attenuators: it is used as bridge and shunt resistance in Bridge-T attenuator.
 Photo Detectors: it detects x-ray and gamma ray photons.

21. Point Contact Devices
A gold or tungsten wire is used to act as the point contact to produce a PN junction region
by passing a high electric current through it. A small region of PN junction is produced
around the edge of the wire which is connected to the metal plate which is as shown in the
figure.

DPP C2(b)

In forward direction its operation is quite similar but in reverse bias condition the wire acts
like an insulator. Since this insulator is between the plates the diode acts as a capacitor. In
general, the capacitor blocks the DC currents when the AC currents are flowing in the circuit
at high frequencies. So, these are used to detect the high frequency signals.

22. Gunn Diode
Gunn diode is fabricated with n-type semiconductor material only. The depletion region of
two N-type materials is very thin. When voltage increases in the circuit the current also
increases. After certain level of voltage, the current will exponentially decrease thus this
exhibits the negative differential resistance.
It has two electrodes with Gallium Arsenide and Indium Phosphide due to these it has
negative differential resistance. It is also termed as transferred electron device. It produces
micro wave RF signals so it is mainly used in Microwave RF devices. It can also use as an
amplifier. The symbol of Gunn diode is shown below:

EXERCISE:

List the types of resistor.
List the type of capacitor.
List the type of diode.

REFERENCE:

1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.

2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.

3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.

4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.

5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.

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Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka

INFORMATION SHEET

PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 02
ELECTRONIC FUNDAMENTAL

WEEK 14

TOPIC 3.0 Automotive Electrical System
SUB-TOPIC 3.1. Electronic components

TOPIC After the lesson, student should be able to:
LEARNING 1. Identify electronic components, symbols and know its function.
OUTCOME 2. Manipulate electronic wiring diagram.
3. React with broken electronic components.
4. Assemble a simple electronic project.
5. Practice using digital and analog multimeter.
6. Practice using digital and analog oscilloscope.

4.5 Transistor
Transistor is symmetrical to a vacuum triode and relatively very small in size. Transistor is
a composition of two words Transfer and Varistor. A transistor consists of three layers of
semiconductor material and each layer is having the capability of transferring current to the
other layers. This three-layer semiconductor device consisting of either two n-type and one
p-type layers of material or two p-type and one n-type layers of material. First type is called
an npn transistor, while the other is called a pnp transistor respectively.
Germanium and silicon are most preferable semiconductor materials which conducts
electricity in semi energetic way. By the process of doping to the semiconductor material,
the result adds additional electrons to the material or produce holes in the material. The
outer layers have widths much greater than the inserted p-type or n-type material that is
typically in 10:1 ratio or less. Lower doping level decreases the conductivity and increases
the resistance of this material, by limiting the number of free carriers.

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The difference between the diode and the transistor is: A diode is made up of two layers
and one junction. Transistor is made of three layers with two junctions. A transistor can acts
as an on/off switch or an amplifier.

Transistor Symbols:

Easy way to remember these transistor symbols is that
 PNP-Points in Permanently
 NPN-Never Points iN
In the symbol of a transistor the arrow indicates the direction of the current flow.
The positive and negative states of voltage and direction of current flow, are always be in
an opposite direction in PNP transistor with respect to NPN transistor. However, the
operation performed by the NPN and PNP transistors are same.

Operation Modes of the Transistor
There are four modes of operations they are saturation, cut-off, active and reverse active.
Saturation Mode: In this mode transistor acts as a switch. From collector to emitter the
current will flow unconditionally (short circuit). Both diodes are in state of forward biased.
Cut-off Mode: In this mode also transistor acts like a switch but there is no current flow from
collector to emitter (open circuit). There is no current flow through both emitter and collector
terminals.
Active Mode: In this mode the transistor acts like an amplifier that is the current from the
collector terminal to emitter terminal is corresponding to the current through the base
terminal. Base will amplify the current moving into the collector terminal and outgoing from
the emitter terminal.
Reverse active Mode: The current from the collector terminal to emitter terminal is
corresponding to the current through the base terminal but this flow is in reverse direction.
Back to Back Connection of a Diode

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The depletion layer developed at pair of junctions namely collector-base and emitter-base
of the transistor mainly due to current carriers only. In the case of two diodes connected
back to back, the formed depletion region cannot pass current carries that are for both
holes and electrons. We already know that due to the thin base layer only the transistor is
working and this layer is nothing but the inserted part of the emitter and collector. Due to
this the emitter and collector comes very impending to each other. When strong electric
field is applied then this grants the majority carriers to pass from the emitter. These majority
carriers will spread as minority carriers over the base and inside the depletion area of the
junction at base-collector. In simple logic, device with one NP junction and one PN junction
that acts like two diodes are placed back to back. At this condition when we apply large
voltages across the base terminal the current cannot flow through the circuit. Because the
applied voltage makes one barrier large and another barrier small from which we cannot
pass the current.
In order to overcome this situation besides the main voltage supply which is placed at the
top of the N-P terminals a small voltage source is added at the lower P-N levels. Due to
this small voltage supply it will push the electrons in to the hole’s part. The main voltage
supply will control the current flow. By these two actions at the depletion layer the current
barriers are reduced. Thus there will be high ascending increase in the voltage through the
transistor.
Types of Transistors
Transistor is the proper arrangement of different semiconductor materials. General
semiconductor materials used for transistor are silicon, germanium, and gallium-arsenide.
Basically the transistors are classified depending on their structure. Each type of transistors
has their own characteristics, advantages and disadvantages.
Some transistors are designed primarily for switching purpose, other side some are
designed for amplification purpose and some transistors are designed for both amplification
and switching purposes. Depending on the structure the transistors are classified into BJT
and FET.

Junction Transistors
Junction transistor is generally called as Bipolar Junction Transistor (BJT). The BJT
transistors have three terminals named emitter (E), Base (B), Collector (C). The name itself
indicates that it has two junctions between p-type and n-type semiconductors. The BJT
transistors are classified in to NPN and PNP transistors depending on the construction.
Unlike FET transistors, the BJT transistors are current-controlled devices. If small amount
of current flows through the base of a BJT transistor, then it causes to flow large current
from emitter to collector. The BJT transistors have low input impedance and it causes to
flow large current through the transistor. The BJT transistors are only the transistors which
are turned ON by the input current which is given to the base. Bipolar junction transistors
can operate in three regions, they are

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 Cut-off Region: Here the transistor is in ‘OFF’ state i.e the current flowing through
the transistor is zero.

 Active Region: Here the transistor acts as an amplifier.
 Saturation Region: Here the transistor is in fully ‘ON’ state and also works as a

closed switch.

NPN Transistor
NPN is one of the two types of Bipolar Junction Transistors (BJT). The NPN transistor
consists of two n-type semiconductor materials and they are separated by a thin layer of p-
type semiconductor. Here the majority charge carriers are electrons and holes are the
minority charge carriers. The flowing of electrons from emitter to collector forms the current
flow in the transistor through the base terminal.
A small amount of current at base terminal causes to flow large amount current from emitter
to collector. Nowadays the generally used bipolar transistor is NPN transistor, because the
mobility of electrons is greater than mobility of holes. The standard equation for the currents
flowing in the transistor is
IE = IB + IC
The symbols and structure for NPN transistors are given below.

PNP Transistor
The PNP is another type of Bipolar Junction Transistors (BJT). The PNP transistors contain
two p-type semiconductor materials and are separated by a thin layer of n-type
semiconductor. The majority charge carriers in the PNP transistors are holes and electrons
are minority charge carriers. The arrow in the emitter terminal of transistor indicates the
flow of conventional current. In PNP transistor the current flows from Emitter to Collector.
The PNP transistor is ON when the base terminal is pulled to LOW with respect to emitter.
The symbol and structure for PNP transistor is shown below.

FET (Field Effect Transistor)
The Field-Effect-Transistor (FET) is another transistors type. Basically the FET transistors
have three terminals they are gate (G), Drain (D) and Source (S). FET transistors are
classified into Junction Field Effect transistors (JFET) and Insulated Gate FET (IG-FET) or
MOSFET transistors. For the connections in the circuit we also consider fourth terminal
called base or substrate. The FET transistors have control on the size and shape of a
channel between source and drain which is created by applied voltage. The FET transistors