Electronics components

and Signals
CHA PT ER 1 ( 1 2 M)

BY: M RS.ISHA S HA H
Introduction
Electronics and its applications
Definition: The branch of engineering which deals with current conduction through a Vacuum or
Gas or Semiconductor is known as Electronics. An electronic device is that in which current flows
through a vacuum or gas or semiconductor. This control of electrons is accomplished by devices
that resist, carry, select, steer, switch, store, manipulate, and exploit the electron.
Or
Electronics deals with electrical circuits that involve active electrical components such as
vacuum tubes, transistors, diodes and integrated circuits, and associated passive
interconnection technologies. Commonly, electronic devices contain circuitry consisting
primarily or exclusively of active semiconductors supplemented with passive elements; such a
circuit is described as an electronic circuit.
Application of Electronics
Communication and Entertainment
 Defense Application
 Industrial Applications
 Medical Science
 Instrumentation
 Basic electronic components
Electronic components are designed to function in specific ways. By adding components to each
other, we can modify the way electricity flows through an electronic device and how it operates.

In the designing of any electronic circuit, three most important considerations are:

I. Circuit components like resistors, Capacitors, Transistors and Diodes.

II. Power sources like dc power supplies and signal generators
III. Measurement and analysis instruments like multimeters and Cathode Ray Oscilloscope
(CRO).
Basic electronic components
They are divided in to two categories:

a) Passive components: The electronic components which transfer the signal from one end to
other end without any change in its strength and shape are called passive components.

Examples of passive components are: Resistors, Capacitors and Inductors.

a) Active components: The electronic components which change the strength and/or shape of the
signal are called as active components.

Examples are diodes and transistors.

Resistor
Definition: Resistor is an electronics component which provides the specifies
amount of opposition (resistance) to the flow of current.
It can be a fixed value or a variable resistor.
Unit: The value of resistor is called resistance. It is denoted by R and the unit of
resistance is Ohms (Ω).
Symbol:

Fixed Resistor Variable Resistor

Resistance
Resistance of material is defined as the opposition to flow of current. It is measured in
Ohms (Ω).
Resistance of metal is small that means they are good conductors of electric current.
But certain material like plastic, wood glass do not allow the current to pass through
them easily, hence they are called as bad conductors or Insulator.
The mathematical expression for resistance of conductor is,
𝒍
𝑹=𝝆
𝒂
Where, 𝝆 = Resistivity of material & it is constant
l = Length of conductor
a = Cross section area
Classification of Resistors
Resistors
◦ Linear
◦ Fixed
◦ Variable
◦ Non Linear
◦ Thermistor (TDR)
◦ Light dependent resistor (LDR)
◦ Voltage dependent resistor (VDR)
Resistors continues………..
Most commonly used resistors in lab are fixed value resistors.

Variable resistors Besides the fixed value resistors, there also exist variable resistors. The
resistance of variable resistors can vary in steps or continuously. Potentiometer is also an
example of continuously varying resistor

Special purpose resistors Light dependent resistors (LDR) and thermistors are examples of
special purpose resistors. Thermistor is a resistor whose value depends on its temperature. It is
also called a heat sensor. LDR is a resistance whose resistance depends upon the amount of light
falling on it.
Color code for resistors
Band color and its value Band color and its
tolerance
Black = 0 Gold = +-5%
Brown = 1 Silver = +-10%
Red = 2 No color means 20%
Orange = 3
Yellow = 4 The first two bands near an end indicate first 2
Green = 5 digits, digit corresponding to 3rd band is the
Blue = 6 power of 10 to be multiplied and fourth band
Violet = 7 indicates tolerance as mentioned in the table.
Grey = 8 Refer fig 1, where brown = 1, black = 0, red = 2
White = 9 and silver = 10 % tolerance. Hence its value is
10 x 10 2 Ω = 1 k Ω.
Capacitors
Capacitors are capable of storing charges. They are used for coupling ac signals from one circuit to
another and for frequency selection etc. A capacitor consists of 2 metallic plates separated by a
dielectric.

The capacitance is defined as : C = Єo Єr A / d,

where A is the area of plates, d is plates separation, Єo is permittivity of free space and Єr is relative
permittivity.

An important parameter for capacitors is its voltage handling capacity beyond which the capacitor
dielectric breaks down.
 Capacitors
There are two main classes of capacitors:

1. Fixed capacitors

 Non electrolytic or normal capacitors: they are mostly of parallel plate type and can
have mica, paper, ceramic or polymer as dielectric.

Electrolytic capacitors: There are two designs of electrolytic capacitors: (i) Axial
where the leads are attached to each end (ii) Radial where both leads are at the same
end.

2. variable capacitors: They have a fixed set of plates and a movable set of plates
which can be moved through a shaft. This movement changes the area of overlap of
the two sets of plates which changes its capacity.
Capacitor Number Code :
A number code is often used on small capacitors where printing is difficult: the 1st number is
the 1st digit, the 2nd number is the 2nd digit, the 3rd number is the power of ten to be
multiplied, to give the capacitance in pF. Any letters just indicate tolerance and voltage rating.
For example: 102 means 10 X 10 2 pF = 1nF and 472J means 4700pF = 4.7nF (J means 5%
tolerance).
Capacitor Colour Code: Sometimes capacitors just show bands like resistors when printing is
tough on them. The colours should be read like the resistor code, the top three colour bands
giving the value in pF. The 4th band and 5th band are for tolerance and voltage rating
respectively. For example: brown, black, orange means 10000pF = 10nF = 0.01µF
 Basic components
Inductors: Inductor is a component made by a coil of wire which is wound on a core. It is used to vary the
impedance of a circuit or for frequency tuning. The value of an inductor depends upon the total number of turns (N),
area of crossection of the core (A) and length of the core (l).The formula is L = μo μr N2 A / l. Its unit is in Henry.

Diode: A diode is a single junction device made of p and n type materials.. Its main function is to rectify an ac signal
although other special purpose diodes like zener are used for voltage regulation in power supplies and led’s are used for
other purposes. A normal diode comes in a black casing whereas a zener diode has a transparent casing.
Basic components
If the pn junction is made between very heavily doped materials then it forms a Zener diode.
These are used for voltage regulation in power supplies.
Light Emitting Diode (LED)
Led’s are pn junction devices which emit light radiation when biased in the forward direction.
Dual colour led’s are also available where two junctions are encapsulated on the same chip.
Basic components
Transistors Transistors are semiconductor devices used for applications like amplification of
voltages, current and are also used in oscillator circuits and switches. It’s a two junction and 3 terminal
device made of three layers of n and p type materials. The three regions are emitter, base and collector.
They are of 2 types (i) pnp and (ii) npn.
INSTRUMENTS
 Multimeter: A multimeter is an instrument which measures electrical parameters such as AC or DC
voltage, current, and resistance. Rather than having separate meters, a multimeter combines a
voltmeter, an ammeter, and an ohmmeter. The two main kinds of a multimeter are analog and
digital.
A digital multimeter has an LCD screen that displays the value of the parameter being measured.
while in an analog multimeter display, a needle moves through a graduated scale. Topmost scale is
usually for resistance and the readings increases from right to left while other scales readings
increase from left to right
INSTRUMENTS:
Cathode ray oscilloscope (CRO): CRO is an instrument which is used
to measure voltages that change with time and to display the
waveforms in real time mode. There is a graphical scale present on the
screen which is used to calculate the voltage or frequency value. A
very important specification of a CRO is its bandwidth which gives
the maximum frequency of a signal which a CRO can measure. A
simple oscilloscope consists of a cathode ray tube, a vertical
amplifier, a time base, a horizontal amplifier and a power supply.
CRO controls from the front panel
 CRO controls from the front panel
Intensity: This knob controls the brightness of the trace by adjusting the number of electrons emerging from the
gun
Focus: This control is for making the trace on the screen sharper. It is connected to the anode of the electron gun
whose voltage collimates the electron beam.
Vertical Position & Horizontal Position: Through these controls the beam can be positioned at variable vertical or
horizontal positions as desired. These knobs apply a dc voltage to the vertical and horizontal deflection plates.
V / Div.: This control is used to control the voltage sensitivity. This is internally connected to an attenuator of the
vertical system. It determines the voltage required by the vertical plates to deflect the beam vertically by one
division.
CRO controls from the front panel
Time / Div This determines the time taken for the spot to move horizontally across one division of
the screen when the sweep is generated by triggering process. The signal which is fed to the vertical
deflection plates provides the triggering to the waveform. Each position of the time/ div knob is applicable
for a particular frequency. This determines the horizontal sensitivity of the observed signal.
Trigger Source This selects the source of the trigger to be applied to the saw tooth waveform. There are
usually three possible sources (i) Internal: This is mostly used for all applications. The vertical signal
applies the triggering signal. (ii) Line: This is generally used when the voltage to be measured is related to
the line voltage. This selects the 50Hz line voltage. (iii) Ext. In this case an external signal is applied
to trigger the saw tooth waveform./
Slope This determines whether the time base circuit responds to the positive or negative slope of the
triggering waveform.
CRO controls from the front panel
AC, DC, GND: This selects the coupling mechanism for the input signal to the CRO. In dc mode the vertical
amplifier receives both ac and dc components of the input signal. In ac mode the coupling capacitor blocks all dc
components and displays only pure ac waveform. In gnd configuration, the input signal is grounded and one gets a
straight line. To measure the dc component of any signal (ac or dc), one has to switch from ac to dc mode and observe
the vertical shift of the waveform. The amount of vertical shift in volts gives the corresponding dc component.
1X-Y mode: In this mode of operation. two signals are superimposed at right angles on each other. The saw
tooth time base circuit is disconnected from the horizontal deflection plates and the external signal which s fed to
channel two is given to time base instead. Hence if two sine waves are fed to two channels respectively then the
electron beam will undergo deflection according to right angle superposition of two sine waves. It will trace lissajous
figures.
Level This determines the amplitude level on the triggering waveform which can start the sweep
Voltage and Current sources
A Source is a device which converts mechanical,
chemical, thermal or some other form of energy
into electrical energy. In other words, the source is
an active network element meant for generating
electrical energy.
The various types of sources available in the
electrical network are voltage source and current
sources.
Examples:
The example of voltage sources is batteries and
alternators.
The example of current sources is photoelectric
cells, collector currents of transistors.
Voltage Source

A voltage source is a two-terminal device whose

voltage at any instant of time is constant and is
independent of the current drawn from it. Such a
voltage source is called an Ideal Voltage Source and
have zero internal resistance.
Practically an ideal voltage source cannot be obtained.
Sources having some amount of internal resistances
are known as Practical Voltage Source. Due to this
internal resistance; voltage drop takes place, and it
causes the terminal voltage to reduce. The smaller is
the internal resistance (r) of a voltage source, the
more closer it is to an Ideal Source.
The symbolic representation of the ideal and practical
voltage source is shown below.
Voltage source
Circuit diagram and characteristics of
Ideal and Practical voltage sources
Current Source
An ideal current source is a two-terminal
circuit element which supplies the same
current to any load resistance connected
across its terminals. It is important to keep in
mind that the current supplied by the current
source is independent of the voltage of source
terminals. It has infinite resistance.
A practical current source is represented as an
ideal current source connected with the
resistance in parallel. The symbolic
representation is shown below:
Circuit diagram and characteristics of
Ideal and Practical current sources
Signal Waveform
Signal parameters
Amplitude (V/I) :The maximum displacement of a wave on either side of its mean position is called
Amplitude.
Time period (T) - Time taken to complete one vibration is called time period, i.e. from A to B.
Frequency(F) : Number of oscillations made by a wave in one second is known as frequency.
Expressed in hertz (Hz or s -1 ) and is given by
F= I/T Hz
Wavelength (λ ): Shortest distance between equivalent points on a continuous wave; measured from
crest to crest or trough to trough. Expressed in meters, centimeters, or nanometers and is given by
λ = C/F
Where, C- speed of light (3x10^8 m/s)
F - frequency of signal
Types of signals
Integrated Circuits
Integrated Circuit (IC) Today all electrical, electronic and computer parts have IC’s in them.
Integrated circuit is a name given to a package which can hold more than 10 and up to millions of
electronic components. They can give various functions like : (i) the function of a full microprocessor circuit
(eg 8085), (ii) a memory chip, (iii) a voltage regulator (LM 7805) or (iv) Can contain just 10 AND gates (eg
LS7400).

For example an IC with name LS 7400 would mean LS series with And gates, LM741C - mA741C is an
operational amplifier (opamp). Datasheets can be referred to, to know the details of pin configurations
and make etc. The pins are usually read starting from left of notch and going anticlockwise.
IC circuit continues…………
Classification of ICs
Based on number of components
Classification of ICs
Advantages of Integrated circuits
The advantages of Integrated Circuits are:
1. Very small size: Hundred times smaller than the discrete circuits.
2. Lesser weight: As large number of components can be packed into a single chip, weight is
reduced
3. Reduced cost: The mass production technique has helped to reduce the price,
4. High reliability: Due to absence of soldered connection, few interconnections and small
temperature rise failure rate is low.
5. Low power requirement: As the size is small power consumption is less.
6. Easy replacement: In case of failure chip can easily be replaced.
Applications
Mixed type applications - cars (automotive controls), televisions, computers, microwaves,
portable devices like laptops, MP3, play stations, cameras, cellular phones to ship equipment's,
aero planes, space craft’s.
These are also used in switching telephone circuits and data processing.
They also found applications in military equipment's.
The most common application of IC is digital watch which tells hour, second, minute, day and
month.
Another common but important application is scientific calculator which can perform basic
functions like addition, subtraction, multiplication and division as well as complex functions like
square root, cube, permutations, combinations , trigonometric functions, etc