109ES: BASIC ELECTRONICS AND INSTRUMENTS

PREPARATION NOTES

BY: PROF. SAURABH SHUKLA

CHAPTER 1 Basic Electronic Devices and Circuits

Topics to be covered:

Introduction to Circuits and It’s Components, Resistance (R), Capacitance (C), Inductors (L), Diode,
LEDs, Transistors, and ICs (Integrated Circuits). Building basic electronics circuits using Ohm’s,
Kirchhoff’s Voltage (KVL) and Kirchhoff’s Current Laws (KCL).

1.1 Introduction to circuits

An electrical circuit is a closed path that allows electricity to flow. It consists of a power source, conductors
(like wires), and a load (like a light bulb or resistor). A circuit must be a complete loop for electricity to
flow; if there's a break (open circuit), the flow stops.

Key Components:

• Power Source:

Provides the electrical energy to drive the circuit, like a battery or a power supply.

• Conductors:

Materials that allow electricity to flow easily, typically wires.

• Load:

A component that uses the electrical energy to perform a function, like a light bulb (producing light), a
resistor (limiting current), or a motor (producing motion).
• Switch:

A component that can open or close the circuit, controlling the flow of electricity.

Types of Circuits:

• Closed Circuit: A complete loop where electricity flows.

• Open Circuit: A break in the loop where electricity cannot flow.

• Series Circuit: Components are connected end-to-end, so the same current flows through each.
 • Parallel Circuit: Components are connected across common points, so the current can split into
different paths.

Circuit Diagrams:

• Circuits are often represented using circuit diagrams that use standardized symbols for different
components.

• For example, a battery is represented by alternating long and short parallel lines, and a resistor is
represented by a zigzag line.

In essence, an electrical circuit is a controlled pathway for electricity to move and perform work.

1.2 Resistance (R)

A resistor (also known as an electrical resistor) is defined as a two-terminal passive electrical element
that provides electrical resistance to current flow. Resistance is a measure of the opposition to the flow
of current in a resistor. The larger a resistor’s resistance, the greater the barrier against the flow of current.
There are many different types of resistors, such as a thermistor.

In an electrical and electronic circuit, the primary function of a resistor is to “resist” the flow of electrons,
i.e., electric current. That is why it is called a “resistor.”

Difference Between Resistance and Resistivity

Parameters Resistance Resistivity

Definition When the flow of electrons is opposed in When resistance is offered

a material is known as resistance

SI unit Ω Ω.m

Symbol R ρ

Dependence Dependent on the length and cross- Temperature

sectional area of the conductor and
temperature
Resistor Circuits (Example Applications)

LED Current Limiting Resistor

Limiting current is very important in an LED. If too much current is flowing through an LED, it will get
damaged. Therefore, a current limiting resistor is used to limit or reduce the current into an LED.

Current limiting resistors are connected in series with an LED to limit the current flowing through the LED
to a safe value. For example, as shown in the image below, the current limiting resistor is connected in series
with the LED.

LED – Current Limiting Resistor Circuit

Resistor Colour Codes

Resistor Colour Codes are used to identify resistive or resistance value and percentage tolerance of any
resistors. The resistor’s colour codes use coloured bands to identify it.

As shown in the figure below, there are four colour bands printed on the resistor. Out of the three bands are
printed side by side, and the fourth band is printed slightly away from the third band.

The first two bands from the left side indicate significant figures, the third band indicates the decimal
multiplier, and the fourth band indicates the tolerance.
The table below shows significant figures, decimal multiplier, and tolerance for different color coding of
resistors.
Color Coding of Resistors

Key Points:

• The Gold and Silver band is always placed to the right.

• The resistor value is always read from left to right.

• If there is no tolerance band, find the side with a band near to a lead and make that the first band.

Example (How to Calculate Resistor Value?)

As shown in the image below, a carbon color-coded resistor has the first ring of green, second of blue, third
of red, and fourth of golden color. Find the specifications of the resistor.

Solution:

As per table of colour coding of resistors,

Green Blue Red Golden

5 6 102 ±5%

Thus, the value of resistance 5600Ω is with ±5% tolerance.

Hence, the value of resistance is in between

5600+5%=5600+280=5880Ω

5600-5%=5600-280=5320Ω

Hence, the value of resistance is in between 5880Ω and 5320Ω.

1.3 Capacitance (C)

What Is a Capacitor?

A capacitor is a two-terminal electrical device that can store energy in the form of an electric charge. It
consists of two electrical conductors that are separated by a distance. The space between the conductors
may be filled by vacuum or with an insulating material known as a dielectric. The ability of the capacitor to
store charges is known as capacitance.

Capacitors store energy by holding apart pairs of opposite charges. The simplest design for a capacitor is a
parallel plate, which consists of two metal plates with a gap between them. But, different types of capacitors
are manufactured in many forms, styles, lengths, girths, and materials.

How Does a Capacitor Work?

For demonstration, let us consider the most basic structure of a capacitor – the parallel plate capacitor. It
consists of two parallel plates separated by a dielectric. When we connect a DC voltage source across the
capacitor, one plate is connected to the positive end (plate I) and the other to the negative end (plate II).
When the potential of the battery is applied across the capacitor, plate I become positive with respect to plate
II. The current tries to flow through the capacitor at the steady-state condition from its positive plate to its
negative plate. But it cannot flow due to the separation of the plates with an insulating material.

An electric field appears across the capacitor. The positive plate (plate I) accumulates positive charges from
the battery, and the negative plate (plate II) accumulates negative charges from the battery. After a point, the
capacitor holds the maximum amount of charge as per its capacitance with respect to this voltage. This time
span is called the charging time of the capacitor.

When the battery is removed from the capacitor, the two plates hold a negative and positive charge for a
certain time. Thus, the capacitor acts as a source of electrical energy.
If these plates are connected to a load, the current flows to the load from Plate I to Plate II until all the
charges are dissipated from both plates. This time span is known as the discharging time of the capacitor.

Standard Units of Capacitance

The basic unit of capacitance is Farad. But, Farad is a large unit for practical tasks. Hence, capacitance is
usually measured in the sub-units of Farads, such as micro-farads (µF) or pico-farads (pF).

Most of the electrical and electronic applications are covered by the following standard unit (SI) prefixes for
easy calculations:

• 1 mF (millifarad) = 10−3 F

• 1 μF (microfarad) =10−6 F

• 1 nF (nanofarad) = 10−9 F
• 1 pF (picofarad) = 10−12 F

Applications of Capacitors:

Capacitors for Energy Storage

Since the late 18th century, capacitors have been used to store electrical energy. Individual capacitors do not
hold much energy, providing only enough power for electronic devices during temporary power outages or
when they need additional power. Many applications use capacitors as energy sources, and a few of them are
as follows:

• Audio equipment
• Camera Flashes

• Power supplies

• Magnetic coils
 • Lasers

Supercapacitors are capacitors that have high capacitances up to 2 kF. These capacitors store large amounts
of energy and offer new technological possibilities in areas such as electric cars, regenerative braking in the
automotive industry and industrial electrical motors, computer memory backup during power loss, and many
others.

Capacitors for Power Conditioning

One of the important applications of capacitors is the conditioning of power supplies. Capacitors allow only
AC signals to pass when they are charged, blocking DC signals. This capacitor effect is used in separating or
decoupling different parts of electrical circuits to reduce noise as a result of improving efficiency. Capacitors
are also used in utility substations to counteract inductive loading introduced by transmission lines.

Capacitors as Sensors

Capacitors are used as sensors to measure a variety of things including humidity, mechanical strain, and fuel
levels. Two aspects of capacitor construction are used in the sensing application – the distance between the
parallel plates and the material between them. The former detects mechanical changes such as acceleration
and pressure, and the latter is used in sensing air humidity.
Capacitors for Signal Processing

There are advanced applications of capacitors in information technology. Capacitors are used by Dynamic
Random Access Memory (DRAM) devices to represent binary information as bits. Capacitors are also used
in conjunction with inductors to tune circuits to particular frequencies, an effect exploited by radio receivers,
speakers, and analog equalizers.

1.4 Inductance (L)

Inductance is the property of an electrical conductor that opposes changes in the electric current flowing
through it. It's a measure of how much a coil or conductor resists changes in current due to the magnetic
field it produces. The unit of inductance is the henry (H).
 • Definition:

Inductance is the tendency of a circuit to oppose any change in the current flowing through it.

• Cause:

When current flows through a conductor, it creates a magnetic field around it. If the current changes, the
magnetic field also changes. This changing magnetic field induces a voltage in the conductor itself, which
opposes the change in current.

• Types:

• Self-inductance: The property of a coil where it opposes changes in current flowing through
itself.
• Mutual inductance: The property of one coil where it opposes changes in current in a
neighbouring coil due to the magnetic field interaction.

• Factors affecting inductance:

• Number of turns: More turns in a coil lead to higher inductance.

• Core material: Materials with higher magnetic permeability increase inductance.

• Coil dimensions: Length and area of the coil influence inductance.

• Inductors:
Inductors are electronic components specifically designed to have inductance and are often used in circuits
to store energy in a magnetic field, filter frequencies, or introduce impedance.

• Lenz's Law:
This law explains how the induced voltage in an inductor opposes the change in current.

• Relationship to magnetic field:

A changing current creates a magnetic field, and this magnetic field, in turn, induces a voltage that opposes
the change in current. This interplay between current, magnetic field, and induced voltage is the essence of
inductance.

1.5 Diode, LEDs, Transistors and ICs

Diodes, LEDs, transistors, and integrated circuits (ICs) are fundamental electronic components. Diodes and
LEDs are two-terminal devices that allow current flow in one direction. Transistors are three-terminal
devices that amplify or switch electronic signals. ICs are multi-terminal components that integrate numerous
transistors and other components onto a single chip for complex functions.

Diodes:
• Function: Diodes are semiconductor devices that allow current to flow in one direction (forward
bias) and block current flow in the opposite direction (reverse bias).
• Structure: They have two terminals: an anode (positive) and a cathode (negative).
• Common Use: Rectification (converting AC to DC), voltage regulation, and signal processing.

LEDs (Light Emitting Diodes):

• Function: LEDs are a type of diode that emits light when current passes through them.

• Structure: Similar to diodes, they have two terminals (anode and cathode).

• Common Use: Indicators, displays, and lighting applications.

• Advantage: Energy efficient and long-lasting,

Transistors:

• Function: Transistors are semiconductor devices that can amplify or switch electronic signals. They
have three terminals: emitter, base, and collector.
• Types: Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs).

• Common Use: Amplification, switching, and signal processing in electronic circuits.

ICs (Integrated Circuits):

• Function:

ICs are small electronic circuits fabricated on a single semiconductor wafer (chip).

• Structure:

They contain numerous transistors, diodes, resistors, and other components, allowing for complex
functionality.

• Common Use:
Microprocessors, memory chips, and various control and processing units in electronic devices.
• Types: Digital ICs, analog ICs, and mixed-signal ICs.
What Is a Diode?

Diodes are used to protect circuits by limiting the voltage and to also transform AC into
DC. Semiconductors like silicon and germanium are used to make the most of the diodes. Even though they
transmit current in a single direction, the way with which they transmit differs. There are different kinds of
diodes and each type has its own applications.

Diode Symbol

A standard diode symbol is represented as above. In the above diagram, we can see that there are two
terminals that are known as anode and cathode. The arrowhead is the anode that represents the direction of
the conventional current flow in the forward biased condition. The other end is the cathode.

Diode Construction
Diodes can be made of either of the two semiconductor materials, silicon and germanium. When the anode
voltage is more positive than the cathode voltage, the diode is said to be forward-biased, and it conducts
readily with a relatively low-voltage drop. Likewise, when the cathode voltage is more positive than the
anode, the diode is said to be reverse-biased. The arrow in the diode symbol represents the direction of
conventional current flow when the diode conducts.

This article lets you understand in detail about various types of diodes.

Types of Diodes

1. Light Emitting Diode

2. Laser diode

3. Avalanche diode

4. Zener diode

5. Schottky diode
6. Photodiode

7. PN junction diode
Light Emitting Diode (LED)

When an electric current between the electrodes passes through this diode, light is produced. In other words,
light is generated when a sufficient amount of forwarding current passes through it. In many diodes, this
light generated is not visible as there are frequency levels that do not allow visibility. LEDs are available in
different colours. There are tricolour LEDs that can emit three colours at a time. Light colour depends on the
energy gap of the semiconductor used.
Laser Diode

It is a different type of diode as it produces coherent light. It is highly used in CD drives, DVDs and laser
devices. These are costly when compared to LEDs and are cheaper when compared to other laser generators.
Limited life is the only drawback of these diodes.

Avalanche Diode
This diode belongs to a reverse bias type and operates using the avalanche effect. When voltage drop is
constant and is independent of current, the breakdown of avalanche takes place. They exhibit high levels of
sensitivity and hence are used for photo detection.

Zener Diode
It is the most useful type of diode as it can provide a stable reference voltage. These are operated in reverse
bias and break down on the arrival of a certain voltage. If current passing through the resistor is limited, a
stable voltage is generated. Zener diodes are widely used in power supplies to provide a reference voltage.

Schottky Diode

It has a lower forward voltage than other silicon PN junction diodes. The drop will be seen where there is
low current and at that stage, voltage ranges between 0.15 and 0.4 volts. These are constructed differently in
order to obtain that performance. Schottky diodes are highly used in rectifier applications.

Photodiode
A photo-diode can identify even a small amount of current flow resulting from the light. These are very
helpful in the detection of the light. This is a reverse bias diode and used in solar cells and photometers.
They are even used to generate electricity.

P-N Junction Diode

The P-N junction diode is also known as rectifier diodes. These diodes are used for the rectification process
and are made up of semiconductor material. The P-N junction diode includes two layers of semiconductors.
One layer of the semiconductor material is doped with P-type material and the other layer with N-type
material. The combination of these both P and N-type layers form a junction known as the P-N junction.
Hence, the name P-N junction diode.

P-N junction diode allows the current to flow in the forward direction and blocks the flow of current in the
reverse direction.

Characteristics of Diode
The following are the characteristics of the diode:

• Forward-biased diode
 • Reverse-biased diode

• Zero biased diode

Forward-biased Diode

There is a small drop of voltage across the diode when the diode is forward-biased and the current is
conducting. For silicon diodes, the forward voltage is 690mV and for germanium, 300mV is the forward
voltage. The potential energy across the p-type material is positive and across the n-type material, the
potential energy is negative.

Reverse-biased Diode

A diode is said to be reverse-biased when the battery’s voltage is dropped completely. For silicon diodes, the
reverse current is -20μA and for germanium, -50μA is the reverse current. The potential energy across the p-
type material is negative and across the n-type material, the potential energy is positive.

Zero-biased Diode

When the diode is zero-biased, the voltage potential across the diode is zero.

Diode Applications
Following are the applications and uses of the diode:

• Diodes as a rectifier

• Diodes in the clipping circuit

• Diodes in clamping circuits

• Diodes in logical gates

• Diodes in reverse current protection

What is LED?

A light-emitting diode (LED) is a semiconductor device that emits light when an electric current flows
through it. When current passes through an LED, the electrons recombine with holes emitting light in the
process. LEDs allow the current to flow in the forward direction and blocks the current in the reverse
direction.

Light-emitting diodes are heavily doped p-n junctions. Based on the semiconductor material used and the
amount of doping, an LED will emit coloured light at a particular spectral wavelength when forward biased.
As shown in the figure, an LED is encapsulated with a transparent cover so that emitted light can come out.

LED Symbol

The LED symbol is the standard symbol for a diode, with the addition of two small arrows denoting the
emission of light.

Simple LED Circuit

The circuit consists of an LED, a voltage supply and a resistor to regulate the current and voltage.

How does an LED work?

When the diode is forward biased, the minority electrons are sent from p → n while the minority holes are
sent from n → p. At the junction boundary, the concentration of minority carriers increases. The excess
minority carriers at the junction recombine with the majority charges carriers.
The energy is released in the form of photons on recombination. In standard diodes, the energy is released in
the form of heat. But in light-emitting diodes, the energy is released in the form of photons. We call this
phenomenon electroluminescence. Electroluminescence is an optical phenomenon, and electrical
phenomenon where a material emits light in response to an electric current passed through it. As the forward
voltage increases, the intensity of the light increases and reaches a maximum.

What determines the colour of an LED?

The colour of an LED is determined by the material used in the semiconducting element. The two primary
materials used in LEDs are aluminium gallium indium phosphide alloys and indium gallium nitride alloys.
Aluminium alloys are used to obtain red, orange and yellow light, and indium alloys are used to get green,
blue and white light. Slight changes in the composition of these alloys change the colour of the emitted light.

Uses of LED

LEDs find applications in various fields, including optical communication, alarm and security systems,
remote-controlled operations, robotics, etc. It finds usage in many areas because of its long-lasting
capability, low power requirements, swift response time, and fast switching capabilities. Below are a few
standards LED uses:

• Used for TV back-lighting

• Used in displays

• Used in Automotives

• LEDs used in the dimming of lights

Types of LED
Below is the list of different types of LED that are designed using semiconductors:

• Miniature LEDs

• High-Power LEDs

• Flash LED

• Bi and Tri-Colour

• Red Green Blue LEDs

• Alphanumeric LED

• Lighting LED
Advantages of LEDs over Incandescent Power Lamps

Some advantages of LEDs over Incandescent Power Lamps are:

• LEDs consume less power, and they require low operational voltage.

• No warm-up time is needed for LEDs.

• The emitted light is monochromatic.

• They exhibit long life and ruggedness.

Transistors

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.
• Collector: It is the positive lead of the transistor.

• Emitter: It is the negative lead of the transistor.

Well, the very basic working principle of a transistor is based on controlling the flow of current through one
channel by varying the intensity of a smaller current that is flowing through a second channel.

Types of Transistors

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

Bipolar Junction Transistor (BJT)

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.
There are three types of configuration, which are common base (CB), common collector (CC) and common
emitter (CE).
In common base (CB) configuration, the base terminal of the transistor is common between input and output
terminals.

In common collector (CC) configuration, the collector terminals are common between the input and output
terminals.

In common emitter (CE) configuration, the emitter terminal is common between the input and the output
terminals.

Field Effect Transistor (FET)

For FET, the three terminals are Gate, Source and Drain. The voltage at the gate terminal can control a
current between the source and the drain. FET is a unipolar transistor in which N-channel FET or P-channel
FET are used for conduction. The main applications of FETs are in low noise amplifiers, buffer amplifiers
and analogue switches.
Other Types

Apart from these, there are many other types of transistors which include MOSFET, JFET, insulated-gate
bipolar transistor, thin-film transistor, high electron mobility transistor, inverted-T field-effect transistor
(ITFET), fast-reverse epitaxial diode field-effect transistor (FREDFET), Schottky transistor, tunnel field-
effect transistor, organic field-effect transistor (OFET), diffusion transistor, etc.

How Do Transistors Work?

Let us look at the working of transistors. We know that BJT consists of three terminals (Emitter, Base and
Collector). It is a current-driven device where two P-N junctions exist within a BJT.
One P-N junction exists between the emitter and base region, and the second junction exists between the
collector and base region. A very small amount of current flow through the emitter to the base can control a
reasonably large amount of current flow through the device from the emitter to the collector.

In the usual operation of BJT, the base-emitter junction is forward-biased, and the base-collector junction is
reverse-biased. When a current flows through the base-emitter junction, the current will flow in the collector
circuit.

In order to explain the working of the transistor, let us take an example of an NPN transistor. The same
principles are used for the PNP transistor, except that the current carriers are holes, and the voltages are
reversed.

Operation of NPN Transistor

The emitter of the NPN device is made of n-type material; hence, the majority of carriers are electrons.
When the base-emitter junction is forward-biased, the electrons will move from the n-type region towards
the p-type region, and the minority carrier holes move towards the n-type region.
When they meet each other, they will combine, enabling a current to flow across the junction. When the
junction is reverse-biased, the holes and electrons move away from the junction, and now, the depletion
region forms between the two areas and no current will flow through it.
When a current flows between the base and emitter, the electrons will leave the emitter and flow into the
base, as shown above. Normally, the electrons will combine when they reach the depletion region.

But the doping level in this region is very low, and the base is also very thin. This means that most of the
electrons are able to travel across the region without recombining with holes. As a result, the electrons will
drift towards the collector.

In this way, they are able to flow across what is effectively a reverse-biased junction, and the current flows
in the collector circuit.

Characteristics of Transistor
Characteristics of the transistor are the plots which can represent the relation between the current and the
voltage of a transistor in a particular configuration.

There are two types of characteristics.

• Input characteristics: It will give us the details about the change in input current with the variation in
input voltage by keeping output voltage constant.
• Output characteristics: It is a plot of output current with output voltage by keeping the input current
constant.
• Current transfer characteristics: This plot shows the variation of the output current with the input
current by keeping the voltage constant.

Input Characteristics
CB Configuration

The following chart will describe the variation of emitter current, IE with base – Emitter voltage,
VBE keeping collector voltage constant, VCB.

CC Configuration

It shows the variation in IB in accordance with VCB with collector-emitter voltage VCE keeping constant.
CE Configuration

Here it shows the variation in IB in accordance with VBE by keeping VCE constant.

Output Characteristics

CB Configuration

This chart shows the variation of collector current, IC with VCB, by keeping the emitter current IE constant.

CC Configuration

This exhibits the variation in IE against the changes in VCE by keeping IB constant.

CE Configuration

Here, it shows the variation in IC with the changes in VCE by keeping IB constant.
Current Transfer Characteristics

CB Configuration

It gives the variation of IC with the IE by keeping VCB as constant.

CC Configuration

This shows the variation of IE with IB by keeping VCE constant.

CE Configuration

Here, it shows the variation of IC with IB by keeping VCE constant.

Advantages of Transistor

• Lower cost and smaller in size.

• Smaller mechanical sensitivity.

• Low operating voltage.

• Extremely long life.

• No power consumption.

• Fast switching.
• Better efficiency circuits can be developed.

• Used to develop a single integrated circuit.

Limitations of Transistors

Transistors have a few limitations, and they are as follows:

• Transistors lack higher electron mobility.

• Transistors can be easily damaged when electrical and thermal events arise. For example,
electrostatic discharge in handling.
• Transistors are affected by cosmic rays and radiation.

Integrated Circuit (ICs)

What is an Integrated Circuit (IC)?

Before the discovery of ICs, the basic method of making circuits was to select the components like diodes,
transistors, resistors, inductors and capacitors and connect them by shouldering. But due to size and power
consumption issues, it was necessary to develop a small size circuit with less power consumption, reliability
and shockproof.

After the invention of the semiconductors and transistors, things were quite simplified to a particular extent,
but the development of integrated circuits changed electronics technology’s face. Jack Kilby from Texas
Instruments and Bob Noyce from Intel are the official creators of integrated circuits, and they did it
independently.

The integrated circuit is a fundamental concept of electronics that builds on other basic concepts previously
discussed in our syllabus.

Definition of Integrated Chip

Integrated circuits are made up of several components such as R, C, L, diodes and transistors. They are built
on a small single block or chip of a semiconductor known as an integrated circuit (IC). All of them work
together to perform a particular task. The IC is easily breakable, so to be attached to a circuit board, it is
often housed in a plastic package with metal pins.

Integrated circuits can function as an oscillator, amplifiers, microprocessors or even as computer memory.

Integrated Circuit Design

An integrated circuit is created using certain logic methods and circuit layouts. The two categories of IC
design are as follows:
 • Analog Design

• Digital Design

• Mixed Design

Digital Design
The digital design approach is used to create integrated circuits (ICs), which are utilised as computer
memories (such as RAM and ROM) and microprocessors. With this approach to design, the circuit density
and overall efficiency are both maximised. The ICs created with this technique operate with binary input
data like 0 and 1. The process for designing digital integrated circuits is depicted in the diagram below.

Analog Design
IC chip is created by using the analogue design process when:

• ICs are utilised as regulators, filters and oscillators.

• Optimal power dissipation, gain and resistance are required.

Mixed Design

The analog and digital design ideas are used in mixed designs. The mixed ICs perform either Analog to
Digital or Digital to Analog conversions.

Integrated Circuit Construction

A complicated stacking of semiconductors, copper, and other related elements to create resistors, transistors,
and other components is an integrated circuit. A die is a combination of these wafers that have been sliced
and moulded.

The ICs’ semiconductor wafers are delicate, and the connections between the layers are extremely complex.
The ICs are packaged because an IC die is too small to solder and connect to. The delicate and tiny die is
transformed into the familiar black chip by the IC packaging.
The connections between the layers are exceedingly complicated, and the semiconductor wafers used to
make the ICs are delicate. Because an IC die is too small to solder, the ICs are packed.
All integrated circuits (ICs) are polarised, and each pin has a specific location and functionality. As seen in
the illustration below, integrated chips employ a notch or a dot to denote the first pin.

The subsequent PINs rise consecutively in a counterclockwise way around the chip after the first pin is
identified.

Integrated Circuit Features

Construction & Packaging

ICs are built with semiconducting components such as silicon. Because of the small size and delicate nature
of IC, a series of tiny gold and aluminium wires are joined together and moulded into a flat block of plastic
or ceramic. Metal pins on the block’s exterior link to cables inside. The solid block stops the chip from
overheating and keeps it cool.

Size of an IC

The size of the integrated chip varies between 1 square mm to more than 200 mm.

Integration of an IC

Because they combine various devices on one chip, integrated chips get their name. A microcontroller is an
integrated circuit (IC) that combines a microprocessor, memory, and interface into a single unit.

Commonly Used ICs

Logic Gate ICs

The combinational circuit generates logical outputs based on a variety of input signals. It may only have two
to three inputs but one output.

Timer ICs
A Timer IC is produced with accurate timing cycles with a 100 % or 50 % duty cycle.
Operational Amplifiers

An OpAmp or an Operational Amplifier is a high gain voltage amplifier with a differential input and a
single-ended output.

Voltage Regulators

A voltage regulator IC provides a constant DC output irrespective of the changes in DC input.

What Are Kirchhoff’s Laws?

In 1845, a German physicist, Gustav Kirchhoff, developed a pair of laws that deal with the conservation of
current and energy within electrical circuits. These two laws are commonly known as Kirchhoff’s Voltage
and Current Law. These laws help calculate the electrical resistance of a complex network or impedance in
the case of AC and the current flow in different network streams. In the next section, let us look at what
these laws state.
 • Kirchhoff’s Current Law goes by several names: Kirchhoff’s First Law and Kirchhoff’s Junction
Rule. According to the Junction rule, the total of the currents in a junction is equal to the sum of
currents outside the junction in a circuit.

• Kirchhoff’s Voltage Law goes by several names: Kirchhoff’s Second Law and Kirchhoff’s Loop
Rule. According to the loop rule, the sum of the voltages around the closed loop is equal to null.

1.6 Kirchhoff’s First Law or Kirchhoff’s Current Law

According to Kirchhoff’s Current Law,

The total current entering a junction or a node is equal to the charge leaving the node as no charge is lost.

Put differently, the algebraic sum of every current entering and leaving the node has to be null. This property
of Kirchhoff law is commonly called conservation of charge, wherein I(exit) + I(enter) = 0.

In the above figure, the currents I1, I2 and I3 entering the node is considered positive, likewise, the currents
I4 and I5 exiting the nodes is considered negative in values. This can be expressed in the form of an equation:

I1 + I2 + I3 – I4 – I5 = 0

A node refers to a junction connecting two or more current-carrying routes like cables and other
components. Kirchhoff’s current law can also be applied to analyse parallel circuits.
Kirchhoff’s Second Law or Kirchhoff’s Voltage Law

According to Kirchhoff’s Voltage Law,

The voltage around a loop equals the sum of every voltage drop in the same loop for any closed network and
equals zero.

Put differently, the algebraic sum of every voltage in the loop has to be equal to zero and this property of
Kirchhoff’s law is called conservation of energy.

When you begin at any point of the loop and continue in the same direction, note the voltage drops in all the
negative or positive directions and returns to the same point. It is essential to maintain the direction either
counterclockwise or clockwise; otherwise, the final voltage value will not be zero. The voltage law can also
be applied in analyzing circuits in series.

When either AC circuits or DC circuits are analysed based on Kirchhoff’s circuit laws, you need to be clear
with all the terminologies and definitions that describe the circuit components like paths, nodes, meshes, and
loops.

Kirchhoff’s Law Solved Example

If R1 = 2Ω, R2 = 4Ω, R3 = 6Ω, determine the electric current that flows in the circuit below.

Solution:

Following are the things that you should keep in mind while approaching the problem:
• You need to choose the direction of the current. In this problem, let us choose the
clockwise direction.

• When the current flows across the resistor, there is a potential decrease. Hence, V =
IR is signed negative.

• If the current moves from low to high, then the emf (E) source is signed positive
because of the energy charging at the emf source. Likewise, if the current moves from
high to low voltage (+ to -), then the source of emf (E) is signed negative because of
the emptying of energy at the emf source.
In this solution, the direction of the current is the same as the direction of clockwise
rotation.
– IR1 + E1 – IR2 – IR3 – E2 = 0
Substituting the values in the equation, we get
–2I + 10 – 4I – 6I – 5 = 0
-12I + 5 = 0
I = -5/-12
I = 0.416 A

The electric current that flows in the circuit is 0.416 A. The electric current is signed
positive which means that the direction of the electric current is the same as the
direction of clockwise rotation. If the electric current is negative then the direction of
the current would be in anti-clockwise direction.