xc

References for Chapter

https://www.electricaltechnology.org/2015/01/resistor-types-resistors-fixed-variable-linear-
non-linear.html#google_vignette
https://byjus.com/physics/resistor/
https://byjus.com/physics/types-of-resistors/
https://uk.rs-online.com/web/content/discovery/ideas-and-advice/resistors-guide
https://www.slideshare.net/slideshow/introduction-to-active-and-passive-
components/118538504#17
https://www.geeksforgeeks.org/electronic-components/

0
 CHAPTER 1 – ELECTRONICS COMPONENTS

- There are several basic electrical components that are commonly found in the circuits. These
components are the fundamental building blocks of electrical and electronic circuits, and can
be found in great numbers on control panels, printed circuit boards, etc.
- They can be used and combined with each other in many different ways to form a new circuit.
- Electrical control system includes the components that are assembled to form a circuit which
are assembled in the control panel must have a specific rating.
- Each component has its data sheet on which details of a component are mentioned.
- Before assembling the electrical circuit, the technician should have detailed knowledge of each
component and its identification.
- Technicians should be able to distinguish the components physically.
- There are some common components which are used in almost every control system, such as,
resistor, capacitor, integrated circuit, light emitting diode, etc. Technicians must know the
characteristics of each component, dependence of each component on different parameters,
basic construction of each component, etc.

❖ Classification of Components:
Electronic components are classified into two groups:
A) Passive Components
B) Active Components

A) Passive Components:
- Passive components are electronic devices that don’t need an external power source to
operate actively. They mainly resist, store, or control the flow of electric current or voltage
in a circuit without actively amplifying or generating signals.
- These Passive components belongs to inactive functions of components, these Passive
components do not have capacity to amplify the voltage or to rectify the supply.
- Without these components assembly of electronic circuit is not possible.
- Resistors, Capacitors, Inductors are called as passive components.

1
 B) Active Components:
- Active components are electronic devices that need an external power source to work. They
actively control and manipulate the flow of electric current in a circuit.
- These components can amplify, switch, or generate electrical signals. These components are
capable of performing active functions like amplification, rectification and switching they are
called as active components.
- They are classified into two groups

● The different types of active components include:

● Diode, Transistor, Integrated circuit are called as active components.

● Electron tubes like vacuum tubes like Diodes, triode.

● Semiconductor devices like diodes, LED, Transistor etc.

1) Resistors :

- Resistor is a fundamental component of an electrical and electronic device.

- In simple words, a resistor opposes the movement of electric charge.
- This opposition is called resistance.
- It has two-ends.
- Resistor controls the current flow, and it also drops the voltage across it, thus lowers the
voltage levels within circuits.
- They are used to limit current, divide voltage, and set biasing conditions in electronic circuits.
- Resistors are again classified into fixed type and variable type components.
- A resistor is a passive two-terminal electrical device that resists the flow of current. It is
probably the simplest element in an electronic circuit.
- It is also one of the most common components as resistance is an inherent element of nearly all
electronic circuits.
- They are usually color-coded.
- Resistors have plenty of applications, but the three most common ones are managing current
flow, dividing voltage, and resistor-capacitor networks.

⮚ Types of Resistors:
- Resistors are classified as a) Fixed Registers b) Variable Registers

2
 a) Fixed Resistors:
- Fixed resistors are resistors with a specific value. Fixed resistors one of the most widely used
types of resistor. Fixed resistors are used in electronics circuits to set the correct conditions in
a circuit.
- Types of Fixed Resistors
- Carbon types ->
a) Carbon Composition Resistors.
b)Carbon film type.
- Wire Wound Resistors
- Thin Metal Film Resistors

1. Carbon Composition Resistors. :

- These resistors are widely used in electronic circuits.
- The carbon composition resistor is also a passive component that restricts the electric current
to a certain extent.
- These are constructed from cylindrical resistive elements that feature embedded metal end
caps.
- The cylindrical resistive element is made from a mixture of ceramic and carbon powder. This
carbon powder has good electrical conductance properties.
- Carbon composition resistor’s value is available from 1Ω to about 20Ω and typical power
ratings are 1/8 W to 2 W.
- These are having low cost and small in size.
- Tinned copper wire leads are inserted in the two ends and structure is sealed with non-
conducting coating.
- The cost of resistor depends on its wattage and not on the value of resistor.

3
Colour coding of Carbon Resistor:

- Resistors may not display the value outside but their resistance can be calculated through their
colour pattern PTH (plated-through-hole) resistors use a colour-coding system (which really
adds some flair to circuits), and SMD (surface-mount-device)resistors have their own value-
marking system.

4
-

5
How to read Resistor Color Code?
The first two bands of resistor show the resistance value of the resistor. And the third band is a
multiplier. If the colored bands on the resistor are green, blue and red. Then value of resistor is 56 ×
100 = 5600Ω i.e. 5.6kΩ.
As I said, some resistors have the fourth band on them. The fourth band shows the tolerance and
mostly seen in high precision resistors. If the colored bands are green, blue, red and brown, then the
value of the resistor would be 56 × 100 = 5600Ω 1% i.e. 5.6kΩ ±1%.
Resistors with high precision also have an extra band for the third digit of their value. So if there are 5
bands on resistance and colored bands are brown, black, black and red then the value will be 100
×100 = 10000Ω = 10kΩ of resistance in the resistor and the fifth band is tolerance. The tolerance band
has increased space between 3 or 4 bands. Now if the last band has a brown color, then tolerance
would be 1% and the resistor value will be 10kΩ ±1%.

2. Wire Wound Resistor:

6
 - Wire wound resistor is made from the insulating core or rod by wrapping around a resistive
wire. The resistance wire is generally Tungsten, manganin, Nichrome or nickel or nickel
chromium alloy and the insulating core is made of porcelain, Bakelite, press bond paper or
ceramic clay material.
- The manganin wire wound resistors are very costly and used with the sensitive test
equipment e.g. Wheatstone bridge, etc. They are available in the range of 2 watts up to 100
watt power rating or more. The ohmic value of these types of resistors is 1 ohm up to 200k
ohms or more and can be operated safely up to 350°C.
- In addition, the power rating of a high power wire wound resistor is 500 Watts and the
available resistance value of these resistors are is 0.1 ohm – 100k Ohms.

Speciality of wire wound resistor:

- Big in size, more power handling capacity. Colour code system is not used.
- Fraction of Ω to 100KΩ and power rating 5 W to 200 W.

b) Variable Resistors
● Variable Resistors consist of a slider which taps onto the main resistor element and a fixed
resistor element. Simply we can say that a variable resistor is a potentiometer with only 2
connecting wires instead of 3.
● Variable resistors are commonly called as rheostats.
● In low current circuit like in electronic circuit, small variable resistors are called as
“potentiometer or pots”. This potentiometer name probably originated from the work
“Potential divider”.
● Variable resistors are normally used in radio or audio equipment for volume control, contrast
and brightness control, contrast and brightness control in TV sets.
● According to material used these resistors are classified into two types:
a) Carbon type and
b) Wire wound type.

7
 a) Carbon Type Potentiometers:
- In this type, a movable metal pointer known as a ‘wiper’ moves on a circular carbon resistive
track.

- Resistive carbon material is deposited on a Bakelite piece.

- Variable resistors always have 3 terminals as shown in fig., Terminal 1 and 3 are fixed
terminals and 2 as variable terminal.

- When terminal 1 and 3 are connected in the circuit, you will get fixed and maximum resistance.

- When 1 and 2 or 2 and 3 terminals are connected you will get variation in resistance when you
rotate the shaft.

- These variable resistors are available in two types.

1) Linear Type 2) Log Type

1) In linear potentiometer resistance varies with linear rate. If you rotate the shaft
suppose for 100 rotation it gives 100Ω at 200 🡪 20 Ω and so on.
2) But in nonlinear potentiometer (log type) resistance varies in log scale, at 10 0 🡪10 Ω ,
200 🡪 100 Ω and 300 🡪 10,000 Ω.
2) Log Type:
- When the maximum range of resistance is required ‘Log type’ pot is preferred.
- Linear type pots are marked with “LIN 10K” and log type with “LOG 10K”.
- when often variation of resistance is required these carbon potentiometers are used like volume
control but when rare adjustment is required small potentiometer called as “presets” are used. The
variation of resistance is done with a screwdriver. The internal construction is similar to that of
potentiometer.
Speciality : Low cost, Used in Radio, TV as volume control, brightness control etc.
Range : 1KΩ to 5MΩ, Power rating 1/2W to 2W.

8
b) Wire wound potentiometers :
- Wire wound potentiometer comprises of several rounds of wire wound around the shaft of the non-
conducting material. The turns of the coil are bonded together by an adhesive.
- Example of this type is rheostat.

- The speciality of such type is high power handling capacity and very small and accurate change
in resistance.
- In wire wound variable resistor non-linear resistor is also available. Non-linearity in the
resistor is achieved by using tapered strip on which resistive wire is wound.
- By sliding the contact, the variation of resistance is achieved. \
- Speciality : High cost, more power handling capacity. Big size.
- Typical range : 100Ω to 1 MΩ, Power rating 2 W to 100 W.

c) Other Resistors :
- Because of large developments in semiconductor technology in addition to diode and
transistors; special type of resistors are manufactured which may be called as active resistors.

i) Thermistor:
- A thermistor is a temperature-sensitive semiconductor that works like a resistor. It's a popular
choice for measuring temperature because it's accurate, cost-effective, and has a high
resistance change per degree of temperature.
- conductors show very small change in resistance but thermistor can increase or decrease its
resistance by more value. hence, thermistor can be NTC or PTC type.
- when resistance decreases with increase in temperature then it is called as “Negative
Temperature Coefficient” of resistance (NTC) and if it increases it is called as “Positive
Temperature Coefficient” of resistance (PTC).
- Thermistors are used in many applications like measurement of temperature, temperature
control, temperature compensation etc.
ii) Light Dependent Resistor (LDR) :
- It is a photosensitive device whose resistance decreases with increase in light intensity.
- Cadmium sulfied material is used for this purpose.
- Its dark resistance is about 100KΩ and it decreases with increase in light.
- LDR is widely used in many applications like automatic street light control, burglar alarm etc.

9
 -
iii) Varistor (VDR):
- It is also a non-linear resistor in which resistance is made variable to voltage.
- It is also known as voltage dependent resistor.
- They are two types,
i) Silicon Carbide VDR,
ii) Metal Oxide VDR.
- Varistors are used in industrial applications and TV circuits for surge suppression.

2) Capacitors:
- It is a Passive Component also called as condenser.
- it is used to store electrical energy (by charging) and to deliver this stored energy (by
discharging).
- it has the capacity of storing charge across it, hence, named as Capacitors.
- They are available in fixed and variable types;
- their capacity measured in “farad”.

10
 ● Types of Capacitors:

- Capacitors can be classified according to the dielectric material used.

- Polar, Non-polar and Fixed/Variable.

1. Fixed Capacitors:
Fixed capacitors can be classified according to dielectric material and polar/non polar such as,
i) Paper Capacitor - Non polar capacitor

- Paper capacitor is manufactured by rolling two thin metal foils (foil is a long strip of metal)
separated by paper roll.
- This is a non-polar capacitor because its polarity is not important.
- It can be connected in either way in the circuit. polarity is not mentioned on the structure of
these capacitors.

-
- As shown in figure, two foils are rolled by placing impregnated paper in between them to form
a cylindrical structure.
- two wire leads are attached to the foils as the connecting terminal. metal plates used here, are
in the form of foils to increase plate area and to minimize the size.

ii) Mica Capacitor:

- The construction is similar to that of paper capacitor only the dielectric material used is mica
foil or mica sheet as shown.

11
 -
iii) Ceramic Capacitor :
- These are commonly observed in many circuits like amplifier, oscillators etc. as coupling
capacitor.
- They are available in many different shapes like disc type, rectangular type, tabular and button
type, tabular and button type as shown as.
- It is a non-polar capacitor.

iv) Aluminum Electrolytic Capacitor.:

- This is a polar capacitor on which polarities are marked as positive and negative.
- Polarity is important because reverse connection may damage the capacitor .
- Another main difference between non-polar and polar is; these capacitors are manufactured in
higher values.
- Higher values are possible because electrolyte is used to provide more capacitance in smallest
space.

12
2) Variable Capacitors:
- Variable capacitor is used in various circuits like tuning circuits of radio, oscillator circuits to
vary the frequency etc. Air is the most common dielectric used in variable capacitor.
1) Air Gang Capacitor:
- Also called as Air Gang condenser.
- This consists of two parallel plates. One of the sets is fixed called as stator and another set is
called as rotor which is fitted on a movable shaft.
- when the shaft is rotated the area covered by each plate of rotor and stator is varied and thus
total capacitance is varied.
- It is used for tuning the radio, large size, high cost but high operating voltage.

❖ Inductor :
- Inductance is the ability of a conductor to produce an induced voltage, when current through it
varies. In other words, the inductor opposes change in current.
- The unit of inductance is “Herry”.
- It is defined as the inductance that will develop a voltage of one volt is across it when current
changes at the rate of one Amper per second or when a voltage of one is induced for the change
of current rate 1 Amp/sec then the inductance of coil i said to be 1 Henry.

13
 - Inductance:
- It is the property of conductor to produce induced voltage, when current varies.

Types of Inductors:
General categories of these inductors are:
1) Fixed Inductors.
2) Variable Inductors.

But they are classified according to the material used for the core.
i) Air core inductors:
- In this, copper wire is wound on a hollow tube of these material. Here Air acts as a core, hence
the name Air-core inductor.
ii) Iron core inductors:
- Here Iron is placed as a former of the coil.
- Iron is a magnetic material, so when AC current flows through a coil the lines of flux are
produced. These lines of
iii) Ferrite core inductors.
- It is an Artificially made non-metallic material.
- When a Ferro-magnetic material is placed in former of the coil the Ferrite core exhibits a
minimum loss of lines of flux.

❖ Transformers:
- It consists of two inductors.
- One of these is for supplying alternating current from an external source and is referred as a
primary winding.
- In transformer, the change in current in one coil can induce an e.m.f. in the second coil.
- The coil in which the voltage is induced is known as secondary winding.
- It is a device, which transfers alternating current of high voltage to low voltage and vice-versa
that’s why it is called as Transformer.

14
 - Working Principle of Transformer.

- A transformer is a static device that transfers electric power between two alternating

current circuits with no change in frequency.

- The Voltage of the circuit can be reduced or increased in accordance with the current

relationship. This is known as stepping up (increasing) the voltage and stepping it

down (decreasing).

 Types of Transformer

Transformer types based on Voltage Level

There are primarily two types of Transformer based on the operating voltage. The following are

some of them:

● Step-down Transformer: The primary voltage is converted to a lower voltage across

the secondary output using a step-down transformer. The number of windings on the

primary side of a step-down transformer is more than on the secondary side. As a

result, the overall secondary-to-primary winding ratio will always be less than one.

Step-down transformer are used in electrical systems that distribute electricity over

15
 long distances and operate at extremely high voltages to ensure minimum loss and

economical solutions. Step-down transformer are used to change high-voltage into

low-voltage supply lines.

● Step-up Transformer: The secondary voltage of a step-up transformer is raised from

the low primary voltage. Because the primary winding has fewer turns than the

secondary winding in this sort of transformer, the ratio of the primary to secondary

winding will be greater than one. Step-up transformer are frequently used in

electronics stabilizers, inverters, and other devices that convert low voltage to a

significantly higher voltage. A step-up transformer is also used in the distribution of

electrical power. For applications connected to power distribution, high voltage is

necessary. In the grid, a step-up transformer is used to raise the voltage level prior to

distribution.

❖ Semiconductor Devices:

- A Semiconductor is a kind of material that performs conductivity between conductors and

insulators and has a conductivity value that lies between the conductor and an insulator.
- Semiconductor materials have some electrical properties that contribute to the operation
of some electronic devices. In this, the resistivity falls as the temperature increases,
whereas metal behaves differently in this term which is oppositely. It helps in the
conduction of electricity in certain situations or conditions but not in all – the integrated
circuits, transistors, and diodes all are made up of semiconductors. Apart from
electricity conduction – it also functions to react to heat and light.

Intrinsic Semiconductor:

- Intrinsic semiconductors are semiconductors that are pure i.e. it does not contain
any impurity.
- Since it does not contain any impurity, the number of free electrons and the number
of holes are equal. It is also known as an i-type semiconductor.
- The number of free electrons and the number of holes depends on the property of
the material and does not depend on the doping.

16
Extrinsic Semiconductor:

Extrinsic semiconductors are intentionally doped with impurity atoms to alter their electrical
properties and increase their conductivity. Doping involves introducing a small number of foreign
atoms into the crystal lattice of the intrinsic semiconductor. The most common dopants are from
Group III (trivalent) and Group V (pentavalent) elements.

There are two main types of extrinsic semiconductors, depending on the type of dopant used:

● N-type Semiconductors

● P-type Semiconductors

N-type Semiconductors
In N-type Semiconductors, the semiconductor material is doped with atoms from Group V of the
periodic table, such as phosphorus (P) or arsenic (As). These dopant atoms have one extra valence
electron compared to the semiconductor material. When they replace some of the semiconductor
atoms, they create extra electrons in the crystal lattice.

● Conductivity is mainly because of electrons.

● The material is entirely neutral.

● The current (I) is due to electron current (Ie), and the concentration of electrons (ne) is
much greater than that of holes (nh).

● Majority carriers are electrons, and minority carriers are holes.

P-type Semiconductors
In order to form p type Semiconductor, trivalent impurity is added to it. These elements have three
electrons in there valence shell and need 1 more electron. These are from Group III of the periodic
table, such as Boron (B) or Aluminum (Al). These dopant atoms have one less valence electron
compared to the semiconductor material. When they are added in semiconductor atoms they take
one electron and create holes in the crystal lattice.

● Conductivity is mainly because of the holes.

● The material is entirely neutral.

● The current (I) is due to hole current (Ih), and the concentration of holes (nh) is much
greater than that of electrons (ne).

● Majority carriers are holes, and minority carriers are electrons.

17
P-N Junction

Inside a semiconductor, a p-n junction is an interface or a border between two semiconductor

material types, namely the p-type and the n-type.

The semiconductor’s p-side, or positive side, has an excess of holes, whereas the n-side, or
negative side, has an excess of electrons. The doping process is used to produce the p-n junction
in a semiconductor.

Formation of P-N Junction

When we utilize various semiconductor materials to form a p-n junction, there will be a grain

boundary that will prevent electrons from moving from one side to the other by scattering

electrons and holes, which is why we employ the doping procedure.

For example, Consider a p-type silicon semiconductor sheet that is very thin. A portion of the p-

type Si will be changed to n-type silicon if a tiny quantity of pentavalent impurity is added. This

sheet will now have both a p-type and an n-type area, as well as a junction between the two.

Diffusion and drift are the two sorts of processes that occur following the creation of a p-n

junction.

18
 - When an electron diffuses from the n-side to the p-side, it leaves an ionized donor on the
n-side, which is stationary.
- On the n-side of the junction, a layer of positive charge develops as the process
progresses.
- When a hole is moved from the p-side to the n-side, an ionized acceptor is left behind on
the p-side, causing a layer of negative charges to develop on the p-side of the junction.
- The depletion area is defined as a region of positive and negative charge on each side of
the junction.
- An electric field direction from a positive charge to a negative charge is generated due to
this positive space charge area on each side of the junction.
- An electron on the p-side of the junction travels to the n-side of the junction due to the
electric field.
- The drift is the name given to this motion. We can observe that the drift current runs in the
opposite direction as the diffusion current.
-

 Biasing Conditions for p-n Junction Diode

In a p-n junction diode, there are two operational regions:

● p-type

● n-type

The voltage applied determines one of three biasing conditions for p-n junction diodes:

● There is no external voltage provided to the p-n junction diode while it is at zero bias.

● Forward bias: The p-type is linked to the positive terminal of the voltage potential,
while the n-type is connected to the negative terminal.

19
 ● Reverse bias: The p-type is linked to the negative terminal of the voltage potential,
while the n-type is connected to the positive terminal.

1) Zero Bias

There is no external voltage provided to the p-n junction diode while it is at zero bias, which

implies the potential barrier at the junction prevents current passage.

2) Forward bias

- When the p-n junction diode is in forwarding bias, the p-type is linked to the positive

terminal of the external voltage, while the n-type is connected to the negative terminal.

- The potential barrier is reduced when the diode is placed in this fashion. When the voltage

is 0.7 V for silicon diodes and 0.3 V for germanium diodes, the potential barriers fall, and

current flows.

- The current grows slowly while the diode is under forwarding bias, and the curve formed

is non-linear as the voltage supplied to the diode overcomes the potential barrier.

- Once the diode has crossed the potential barrier, it functions normally, and the curve rises

quickly as the external voltage rises, yielding a linear curve.

3) Reverse Bias

- When the PN junction diode is under negative bias, the p-type is linked to the negative

terminal of the external voltage, while the n-type is connected to the positive terminal.

- As a result, the potential barrier becomes higher. Because minority carriers are present at

the junction, a reverse saturation current occurs at first.

- When the applied voltage is raised, the kinetic energy of the minority charges increases,

affecting the majority charges. This is the point at which the diode fails. The diode may be

destroyed as a result of this.

 Rectifier

20
Rectifier is an electronic component that converts alternating current (AC) into direct current

(DC), ensuring a unidirectional flow of electric charge.

❖ Half-Wave Rectifier

➢ The simplest type of rectifier.

➢ Uses a single diode to allow current to flow in only one direction during one half-

cycle of the AC waveform.

➢ Efficiency is relatively low.

Half Wave Rectifier

It is easy to construct. Similar to rectifier Half way rectifier is used to convert AC (Alternating

Current) signal into DC (Direct Current) signal by passing through negative or positive half cycle.

The only drawback is it is less efficient by comparing to full-wave rectifier. In simple words Half

wave rectifier produces purely positive by avoiding negative half-cycle on the other hand full

wave rectifier produces purely negative half cycle by changing the direction. The efficiency of half

wave rectifier is 40.5% which is considered as lower than full wave rectifier.

Half Wave Rectifier Circuit

Circuit for Half Wave Rectifier is given below:

21
Types of Semiconductor Diode

There are different types of semiconductor diodes that are used widely in our daily life some of

which are,

- LED

- Zener Diode

- Photodiode

- Schottky Diode

1. LED

LED is also called a Light Emitting Diode, it is the most useful kind of diode when the diode is

attached in forwarding bias, the then-current that flows through the junction produces light and

hence they are widely used as bulbs for providing light.

2. Zener Diode

Zener diode is a type of diode, that allows the flow of current in a forward direction, and it can

also work in reverse conditions, the Zener diode has an application in voltage regulation, The

Zener diode is a heavily doped p-n junction diode made to work in reverse bias condition.

3. P-N Junction Diode

22
P-N junction diodes also called rectifier diodes are used for the rectification process. In a P-N

junction diode, two layers of semiconductors materials are used. For a P-N junction diode, one

layer is made of P-type semiconductor material and the other layer of N-type material. The

combination of these two layers forms a junction known as the P-N junction. Thus, the name

comes P-N junction diode.

The current in the P-N junction diode flows in the forward-biased condition and blocks in the

reverse-biased condition.

4. Schottky Diode

Schottky Diodes are special P-N junction diodes that are made to work in low-voltage regions

ideally in voltage ranges between 0.15 and 0.4 volts. These are made differently to obtain

maximum performance at low voltage. Schottky diodes are highly used in rectifier applications.

❖ Transistors:

- A transistor is a type of semiconductor device that can be used to conduct and insulate
electric current or voltage. A transistor basically acts as a switch and an amplifier. In simple
words, we can say that a transistor is a miniature device that is used to control or regulate
the flow of electronic signals.
- The name Transistor is made up of two terms “transfer of Resistor” because its resistance
transfers from one value to other depending on its bias.

Transistor consists of three layers each of which can carry a current. If the transistor is working as

an amplifier then it transforms a small input current into a big output current.

● In the case of a switch, it can be one of any two states that are ON or OFF to control
the flow of electronic signals through an electronic device.

● A transistor is of three layers or we can say three terminals and each of them carries
the current.

PNP Transistor
23
A PNP transistor is a type of bipolar junction transistor that consists of three layers of semiconductor
material. It has a N-type layer sandwiched between the two P-type layers. PNP transistors are widely
used in electronic circuits for amplification and signal processing.

NPN Transistor

An NPN Transistor is a Negative-Positive-Negative transistor that has a significant and varied

impact on electronic circuits. The NPN transistor is made up of three semiconductor layers that are

arranged in a particular way. One of the layers is of the negative (N) type and is sandwiched

between two of the positive (P) types.

Parts of a Transistor

A typical transistor is composed of three layers of semiconductor materials or, more specifically,
terminals which help to make a connection to an external circuit and carry the current. A voltage or
current that is applied to any one pair of the terminals of a transistor controls the current through the
other pair of terminals. There are three terminals for a transistor. They are listed below:

● Base: This is used to activate the transistor. It is heavily doped and medium in size.
● Collector: It is the positive lead of the transistor. It is lightly doped and thin in size.
● Emitter: It is the negative lead of the transistor. It is Medium doped and larger in size.

Types of Transistors

There are mainly two types of transistors, based on how they are used in a circuit.

Bipolar Junction Transistor (BJT)

24
The three terminals of BJT are the base, emitter and collector. A very small current flowing
between the base and emitter can control a larger flow of current between the collector and emitter
terminal.

Furthermore, there are two types of BJT, and they include:

● P-N-P Transistor: It is a type of BJT where one n-type material is introduced or placed
between two p-type materials. In such a configuration, the device will control the flow of
current. PNP transistor consists of 2 crystal diodes which are connected in series. The right
side and left side of the diodes are known as the collector-base diode and emitter-base
diode, respectively.
● N-P-N Transistor: In this transistor, we will find one p-type material that is present between
two n-type materials. N-P-N transistor is basically used to amplify weak signals to strong
signals. In an NPN transistor, the electrons move from the emitter to the collector region,
resulting in the formation of current in the transistor. This transistor is widely used in the
circuit.

❖ SMPS (Switch Mode Power Supply) :

- A switching regulator is integrated into an electronic power supply called a switch mode
power supply (SMPS), which is sometimes referred to as a switcher, switched power
supply,

25
 - switching-mode power supply, and simply switcher. This power supply effectively
converts electrical power.
- An SMPS, like other kinds of power supplies, converts current and voltage characteristics
while transferring power from an AC or DC source (often mains power; see AC adapter)
into DC loads, like a personal computer.
-
-
- A switching regulator is included in an electronic power supply called a switched-mode

power supply (SMPS) to facilitate effective electrical power conversion.

- An SMPS converts voltage and current while transferring power to DC loads via a DC or

AC source, just like other suppliers.

Working Principle of SMPS

- Switching regulators are employed in SMPS devices to maintain & regulate the output

voltage by turning on or off the load current.

- The mean value between on and off is the appropriate power output for a system.

- The SMPS reduces depletion strength because, in contrast to the linear power supply, it

carries transistor switches between low dissipation, full-on as well as full-off phases and

spends significantly fewer seconds in high dissipation cycles.

Working

The working of SMPS can be understood by the following figure.

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Benefits of SMPS

● The switch-mode power source is small in scale.

● The SMPS is very lightweight.
● SMPS power consumption is typically 60 to 70 per cent, which is ideal for use.
● SMPS is strongly anti-interference.
● The SMPS production range is large.

Limitations of SMPS
● The complexity of SMPS is very large.
● The production reflection is high and its control is weak in the case of SMPS.
● Use of SMPS can only be a step-down regulator.
● In SMPS, the voltage output is just one.

Classification of IC’s:

What is an Integrated Circuit?

When several electronic circuit components like transistors, diodes, resistors,

capacitors, etc. are fabricated and interconnected on a single chip of semiconductor
material (usually silicon or germanium) to form a circuit, it is referred to as an
integrated circuit (IC). Since, several components are integrated on a single chip,
due to which it named so.

- The IC’s are classified into two groups.

- These digital IC’s can be classified according to the semiconductor device, which
is basically used as basic block in manufacturing process of microprocessor and
other IC’s.
- These IC’s are-
1. RTL = Resistor Transistor Logic Family
2. DTL = Diode Transistor Logic Family

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 3. TTL = Transistor Transistor Logic Family
4. ECL = Emitter Coupled Logic Family
5. NMOS = N-channel MOSFET family
6. PMOS = P-channel MOSFET family
7. CMO

 Characteristics of Digital ICs

On moving towards the characteristics – they are temperature sensitive in nature and the rest other

are Some important characteristics or parameters are given as follows:

1. Speed of Operation(Delay)

- The speed of a digital circuit is expressed in terms of propagation delay.

- The delay times are measured between the 50% voltage levels of input and output.

- The propagation delay is defined as “The time required to change the output from one
logic state to other logic state after input is applied.

- It is denoted as “tp”.

- for example, TTL logic family has tp = 10 ns, specifying that it takes 10 nanosec time to
change the output from one state to other state.

2. Power Dissipation
- Any digital circuit requires some power for operation. This is the amount of power dissipated
in an IC.
- It is determined by the current an IC draws from the VCC supply, it is expressed by VCC x
ICC. This power is specified in milliwatts.
- It is shown in Fig.2 that when the gate is in the HIGH output as shown in Fig.2(a), the current
drawn by the gate is represented by ICCH. Similarly, in the LOW output, the current drawn
by ICCL is in Fig.2(b).
-

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 -
3. Figure Of Merit:
- The figure of merit is defined as the product of speed and power. The speed of the logic
circuit is specified in terms of propagation delay, so the figure of merit is specified in
milliwatts.

Figure of merit = propagation delay x power

4. Fan In - Fan Out:

- Fan Out
- Fanout is the maximum number of similar logic gates that a gate can drive without any
degrading in voltage levels. High fanout is advantageous because the need for additional
drivers to drive more gates is less. It is used to derive the logical inputs for the working and
it means the maximum number of standard logic inputs which an be derive efficiently.
- Fan In
- It is defined as the number of inputs that can be connected to a gate. For example, 7400
represents two input NAND gates, therefore fan-in of 7400 is 2. So it is basically the number
of input it can handle properly for the procedure or working.

Difference between CMOS and TTL

Characteristics CMOS TTL

Voltage Levels Wide range of voltage levels Fixed voltage levels (typically
5V)

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Power Low High
Consumption

Technology MOSFET Bipolar Junction Transistor

(BJT)

Noise High Low

Immunity

Fan-Out High fan-out capability Lower fan-out capability

Capability

Speed Slow propagation delays Fast propagation delays

Power Supply Typically operates at 5V or 3.3V Typically operates at 5V

Applications Battery-operated devices, high- High-speed applications,

density ICs memory systems

 Characteristics of Electronic components :

Electronic
Component Advantages Disadvantages

● It is used to control voltage and

current in electrical circuit.
● It produces heat when
● Low cost.
Resistor current flow in it.
● It Provide precise resistance
● It does not store energy.
value
● Widely available in Market.

● It stores electrical energy in it. ● It stores limited energy

● It is used in timing circuits. only.
Capacitor
● It is used to stabilize voltage in ● It may leak its charge over
circuit. time.

Inductor ● It stores electrical energy in it. ● It can be heavy.

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Electronic
Component Advantages Disadvantages

● It is used in transformers. ● It causes voltage spikes

● It is used to stabilize voltage in when current in the circuit
circuit. changes.

● It is used in changing the

● It can be heavy
voltage.
Transformer ● It is only limited to AC
● It offers isolation between input
circuits.
and output in circuits.

● It acts a amplifier or switch in ● It requires proper

circuit. configuration.
Transistor
● It acts as a key component in ● It is sensitive to
amplifiers. environmental factors.

● It combines multiple electronic ● It is complex to

Integrated components. troubleshoot.
Circuit (IC) ● It reduces component size ● It offers limited
● It reduces power consumption. customization.

● It allows current in only one

direction. ● It limits to only one-way
● It is used for rectifying AC circuit current flow.
Diode
to DC circuit. ● It drops voltage across the
● It protects circuit from reverse diode.
voltage.

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