Introduction and importance of the electrical project LECTURE_PPTS.ppt

SSGMCE, Shegaon
Electronic Devices And
Circuits
Lecture 01
Introduction & Importance of the Subject
Prof. A. N. Dolas, Dept. of E&TC

Introduction
• Why the name ‘electronics’?
 I mean why not protonics or neutronics?

Introduction Contd.
• What is electronics?
 The IRE has defined electronics in proceedings of
IRE vol.38(1950) as that:
“ The Field of Science & Engineering, which deals
with the study, design and use of devices, which
depends on the conduction of electricity through a
vacuum, gas or semiconductor”.

Beginning and Development of
Electronics
• 1850- German scientist Geissler
 If the air is removed from a glass tube, it
glows when an electric current passes through
it.
• 1878- British scientist, Sir William Crookes
 The current in vacuum tubes seemed to consist
of particles.

Electronics Contd..
• 1897- Electron is discovered
• French physicist, Perrin demonstrated that current in
a vacuum tube consists of the movement of
negatively charged particles in a given direction.
Some of the properties of these particles were
measured by British physicist Thomson.
• These negatively charged particles were later
on, named as electrons

Electronics Contd..
• 1909- An American physicist
Measured the charge on an electron.
Result of these discoveries, the movement of
electron could be controlled, and thus the
electron era started.

Electronics Contd..
• 1904-Fleming(Fleming Tube or diode vacuum
tube)
Invented a vacuum tube that allowed electrical
current only in one direction.
• 1907- An American Scientist Lee deForest
Invented a tube, which could amplify weak
electrical signals. Named as Triode vacuum
tube. Prof. A. N. Dolas, Dept. of E&TC

Electronics Contd..
• Around 1915- Triode vacuum tube used in
oscillator circuit and telephone system.
• 1916-Tetrode invented by a German engineer.
• 1926- Pentode invented by a Dutch engineer.

Electronics Contd..
• 1920- Invented first TV picture tube, called the
Kinescope, by an American researcher.
• Several types of microwave tubes were
invented during world War II.

Electronics Contd..
• 1947- Walter Britain, John Bardeen and
William Shockley
Invented transistor at Bell laboratory
(America).
Produced commercially in 1951.
• 1959-Robert Noyce given an idea for making
multiple devices on a single piece of silicon.

Functions
• Rectification (DC Generation)
• Amplification
• Control
• Generation (Oscillators)
• Conversion of light into electricity
• Conversion of electricity into light

Syllabus
• Diode
• Transistor
• Transistorized circuits
• Special purpose diodes
• FET, UJT

Importance of Subject
• Basic subject in Electronics engineering.
• Subject plays vital role to understand
electronics and communication.
• Thorough understanding of this subject will
provide the strong platform to the student for
study of higher-level electronics.

SNo. Title Author Publication
T-1 Electronics
Devices & Circuits
Jacob Milman
and Christos C.
Halkies
Tata McGraw Hill
Book Co.,
New Delhi.
T-2 Electronics
Devices & Circuits
Allen
Mottershead
Prentice Hall of
India Private
Limited,
New Delhi.
T-3 Electronics
Devices & Circuits
Boylestad R. Prentice Hall of
India Private
Limited,
New Delhi.
T-4 Applied Electronics R.S. Sedha S-chand
Publications,
NewDelhi.

SNo. Title Author Publication
R-1 Basic Electronics Bernard Grob Tata Mc-Graw Hill
Publishing Company,
New Delhi.
R-2 Basic Electronics
Solid State
B. L. Thereja
R-3 Microelectronic
Circuits Theory
and Applications
Adel S. Sedra
Kenneth C.
Smith
Oxford university
press

Basic Electronics
Things to be covered:
• What is electricity
• Voltage, Current, Resistance
• Ohm’s Law
• Capacitors, Inductors
• Semiconductors
• Mechanical Components
• Digital Electronics

What is Electricity
• Everything is made of atoms
• There are 118 elements, an atom is a single part of an
element
• Atom consists of electrons, protons, and neutrons

• Electrons (- charge) are attracted to protons (+ charge), this
holds the atom together
• Some materials have strong attraction and refuse to loss
electrons, these are called insulators (air, glass, rubber, most
plastics)
• Some materials have weak attractions and allow electrons to be
lost, these are called conductors (copper, silver, gold,
aluminum)
• Electrons can be made to move from one atom to another, this
is called a current of electricity.

• Surplus of electrons is called a
negative charge (-). A shortage
of electrons is called a positive
charge (+).
• A battery provides a surplus of
electrons by chemical reaction.
• By connecting a conductor
from the positive terminal to
negative terminal electrons will
flow.

Voltage
• A battery positive terminal (+) and a negative terminal (-). The
difference in charge between each terminal is the potential
energy the battery can provide. This is labeled in units of volts.
Water Analogy

Voltage Sources:

• Voltage is like differential pressure,
always measure between two points.
• Measure voltage between two points
or across a component in a circuit.
• When measuring DC voltage make
sure polarity of meter is correct,
positive (+) red, negative (-) black.

Ground

Exercise
• Measure DC voltage from power supply using multimeter
• Measure DC voltage from power supply using oscilloscope
• Measure DC voltage from battery using multimeter
• Measure AC voltage from wall outlet using a multimeter
• Measure AC voltage from wall outlet using an oscilloscope
Effective or Root Mean Square Voltage
(Measured with multimeter)
ERMS=0.707xEA
E

Current
• Uniform flow of electrons thru a circuit is called current.
WILL USE CONVENTIONAL FLOW NOTATION ON
ALL SCHEMATICS

• To measure current, must break circuit and install meter in line.
• Measurement is imperfect because of voltage drop created by meter.

Resistance
• All materials have a resistance that is dependent on cross-
sectional area, material type and temperature.
• A resistor dissipates power in the form of heat

Various resistors types

When measuring resistance, remove
component from the circuit.

Resistor Color Code

• Determine the resistance of various resistors of unknown
value using the resistor color code
• Using the multimeter, compare the specified resistance and
measured resistance
• Using the multimeter to examine the characteristics of various
potentiometers
Exercise

Ohm’s Law

Prototyping Board
Example of how components are
Inserted in the protoboard

Exercise
• Calculate the total current and voltage drop across each resistor shown in Figure 1
• Build the circuit in Figure 1 on the prototype board
• Measure the total circuit current and voltage drops across each resistor and compare
the calculated and measured values

Capacitance
Battery
Capacitor
Unit = Farad
Pico Farad - pF = 10-12F
Micro Farad - uF = 10-6F
A capacitor is used to store charge for a short amount of time

Capacitor Charging

Capacitor Discharge

Inductance

Discussion!!

SSGMCE, Shegaon
Circuits
Lecture 02
Atomic Structure

Electrons in Isolated Atoms
• Isolated atoms have energy levels
– The electrons can only be found in these
energy states

Atoms in Solids
• Atoms form a lattice structure
The lattice affects the structure of the energy levels of each
atom – we now have joint levels for the entire structure

Intrinsic Semiconductor
• Elemental or pure semiconductors have equal
numbers of holes and electrons
– Depends on temperature, type, and size.
• Compound Semiconductors can be formed from
two (or more) elements (e.g., GaAs)

Extrinsic Semiconductors
• A pure semiconductors where a small
amount of another element is added to
replace atoms in the lattice (doping).
– The aim is to produce an excess of either
electrons (n-type) or holes (p-type)
– Typical doping concentrations are one part in
ten million
– Doping must be uniform throughout the lattice
so that charges do not accumulate

N-Type and P-Type
• One valence electron too many (n-type)
– Arsenic, antimony, bismuth, phosphorus
• One valence electron too few (p-type)
– Aluminum, indium, gallium, boron

What Are Diodes Made Out Of?
• Silicon (Si) and Germanium (Ge) are the two most
common single elements that are used to make Diodes.
A compound that is commonly used is Gallium
Arsenide (GaAs), especially in the case of LEDs
because of it’s large bandgap.
• Silicon and Germanium are both group 4 elements,
meaning they have 4 valence electrons. Their
structure allows them to grow in a shape called the
diamond lattice.
• Gallium is a group 3 element while Arsenide is a group
5 element. When put together as a compound, GaAs
creates a zincblend lattice structure.
• In both the diamond lattice and zincblend lattice, each
atom shares its valence electrons with its four closest
neighbors. This sharing of electrons is what ultimately
allows diodes to be build. When dopants from groups
3 or 5 (in most cases) are added to Si, Ge or GaAs it
changes the properties of the material so we are able
to make the P- and N-type materials that become the
diode.
Si
+4
Si
+4
Si
+4
Si
+4
Si
+4
Si
+4
Si
+4
Si
+4
Si
+4
The diagram above shows the
2D structure of the Si crystal.
The light green lines
represent the electronic
bonds made when the valence
electrons are shared. Each Si
atom shares one electron with
each of its four closest
neighbors so that its valence
band will have a full 8
electrons.

N-Type Material
N-Type Material: When extra valence electrons are introduced
into a material such as silicon an n-type
material is produced. The extra valence
electrons are introduced by putting
impurities or dopants into the silicon. The
dopants used to create an n-type material
are Group V elements. The most commonly
used dopants from Group V are arsenic,
antimony and phosphorus.
The 2D diagram to the left shows the extra
electron that will be present when a Group V
dopant is introduced to a material such as
silicon. This extra electron is very mobile.
+4
+4
+5
+4
+4
+4
+4
+4
+4

P-Type Material
P-Type Material: P-type material is produced when the dopant
that is introduced is from Group III. Group
III elements have only 3 valence electrons
and therefore there is an electron missing.
This creates a hole (h+), or a positive charge
that can move around in the material.
Commonly used Group III dopants are
aluminum, boron, and gallium.
The 2D diagram to the left shows the hole
that will be present when a Group III dopant
is introduced to a material such as silicon.
This hole is quite mobile in the same way the
extra electron is mobile in a n-type material.
+4
+4
+3
+4
+4
+4
+4
+4
+4

SSGMCE, Shegaon
Circuits
Lecture 03 & 04
Semiconductor Diode

The PN Junction
Steady State1
P n
- - - - - -
- - - - - -
- - - - - -
- - - - - -
- - - - - -
+ + + + + +
+ + + + + +
+ + + + + +
+ + + + + +
+ + + + + +
Na Nd
Metallurgical
Junction
Space Charge
Region
ionized
acceptors
ionized
donors
E-Field
+
+
_ _
h+ drift h+ diffusion e- diffusion e- drift
= =

The PN Junction
Steady State
P n
- - - - -
- - - - -
- - - - -
- - - - -
+ + + + +
+ + + + +
+ + + + +
+ + + + +
Na Nd
Metallurgical
Junction
Space Charge
Region
ionized
acceptors
ionized
donors
E-Field
+
+
_ _
h+ drift h+ diffusion e- diffusion e- drift
= =
= =
When no external source
is connected to the pn
junction, diffusion and
drift balance each other
out for both the holes
and electrons
Space Charge Region: Also called the depletion region. This region includes
the net positively and negatively charged regions. The space charge region
does not have any free carriers. The width of the space charge region is
denoted by W in pn junction formula’s.
Metallurgical Junction: The interface where the p- and n-type materials meet.
Na & Nd: Represent the amount of negative and positive doping in number of
carriers per centimeter cubed. Usually in the range of 1015 to 1020.

The Biased PN Junction
P n
+
_
Applied
Electric Field
Metal
Contact
“Ohmic
Contact”
(Rs~0)
+
_
Vapplied
I
The pn junction is considered biased when an external voltage is applied.
There are two types of biasing: Forward bias and Reverse bias.
These are described on then next slide.

The Biased PN Junction
Forward Bias: In forward bias the depletion region shrinks slightly in
width. With this shrinking the energy required for
charge carriers to cross the depletion region decreases
exponentially. Therefore, as the applied voltage
increases, current starts to flow across the junction.
The barrier potential of the diode is the voltage at which
appreciable current starts to flow through the diode.
The barrier potential varies for different materials.
Reverse Bias: Under reverse bias the depletion region widens. This
causes the electric field produced by the ions to cancel
out the applied reverse bias voltage. A small leakage
current, Is (saturation current) flows under reverse bias
conditions. This saturation current is made up of
electron-hole pairs being produced in the depletion
region. Saturation current is sometimes referred to as
scale current because of it’s relationship to junction
temperature.
Vapplied > 0
Vapplied < 0

Properties of Diodes
Figure 1.10 – The Diode Transconductance Curve2
• VD = Bias Voltage
• ID = Current through
Diode. ID is Negative
for Reverse Bias and
Positive for Forward
Bias
• IS = Saturation
Current
• VBR = Breakdown
Voltage
• V = Barrier Potential
Voltage
VD
ID (mA)
(nA)
VBR
~V
IS

SSGMCE, Shegaon
Circuits
Lecture 05
Energy Band Structure

Band Theory
• Three bands of energy levels form
– Valence Band – most of the electrons are
here
– Conduction Band – electrons here give the
material electrical conductivity
– Forbidden Band – electrons must jump this
band to get from the valence to the
conduction band

Lattice Bands

Properties of Diodes
The Shockley Equation
• The transconductance curve on the previous slide is characterized by
the following equation:
ID = IS(eVD/VT – 1)
• As described in the last slide, ID is the current through the diode, IS is
the saturation current and VD is the applied biasing voltage.
• VT is the thermal equivalent voltage and is approximately 26 mV at room
temperature. The equation to find VT at various temperatures is:
VT = kT
q
k = 1.38 x 10-23 J/K T = temperature in Kelvin q = 1.6 x 10-19 C
•  is the emission coefficient for the diode. It is determined by the way
the diode is constructed. It somewhat varies with diode current. For a
silicon diode  is around 2 for low currents and goes down to about 1 at
higher currents

Resistivity
R
T
Conductor
Semiconductor

Conduction
• In order for an electron to become free and
participate in current flow, it must gain enough
energy to jump over the forbidden band
• For semiconductors at room temperature, there
is not enough energy to conduct.
• As temperature increases more electrons have
the energy to jump the forbidden band
– Resistivity decreases
– This is the opposite behavior of conductors

Semiconductors
• When an electron becomes free, it creates
a “hole” in the lattice structure
A hole is effectively a positive charge

Electron and Hole Movement

SSGMCE, Shegaon
Circuits
Lecture 06
Biasing Diode

In a dc circuit

The PN Junction Diode
Start with a P and N type material.
Note that there is excess negatives
in the n-type and excess positives
in the p-type
Merge the two – some of the negatives
migrate over to the p-type, filling in the
holes. The yellow region is called the
depletion zone.
More positive
than rest of N
More negative
than rest of P

Biasing the Junction
Apply a voltage as indicated. The free
charge carriers (negative charges in the N
material and positive charges in the P
material) are attracted to the ends of the
crystal. No charge flows across the
junction and the depletion zone grows.
This is called reverse bias.
Switch polarity. Now the negative
charges are driven toward the junction in
the N material and the positive charges
also are driven toward the junction in the
P material. The depletion zone shrinks
and will disappear if the voltage exceeds
a threshold. This is called forward bias.

Diode Circuit Symbols
Reverse Bias Forward Bias
N material (cathode)
P material (anode)

I-V Curve
Recall Ohm’s Law (V=IR) Put it into slope-intercept form
to get I = V/R. The slope of the graph is 1/R. Large slopes
mean small R.

Types of Diodes
• Rectifier Diode
– Used in power supplies
• Signal Diode
– Used in switches, detectors, mixers, etc.
• Zener Diode
– Voltage regulation – operated reverse bias in
the avalanche region
• Reference Diode
– Used like zener for voltage regulation

Types of Diodes
• Varactor Diode
– PN junction exhibits capacitive properties
• Depletion zone acts like a dielectric
• Adjacent material acts like the capacitor plates
– Increasing reverse bias decreases capacitance
– recall
– Capacitance Effect is destroyed if the forward
bias is great enough to destroy the depletion
zone
d
A
C o



SSGMCE, Shegaon
Circuits
Lecture 08
Zener Diode

Precise Voltage Regulation
• If the load current is varying, but you
require voltage to be constant, R must
vary (V=IR).

The Avalanche Region
• Increasing reverse bias on the diode
eventually accelerates electrons in the
depletion zone so that they ionize other
atoms.
– The freed electrons ionize other atoms
– Avalanche occurs
• Zener Diodes are designed so that the
transition potential is very steep

Zener I-V Curve
For a large change of current, voltage remains at VZ
Zener acts like an automatically varying resistor.
Can be obtained with VZ from 2.4 – 200 V.

Zener Regulation Circuit
Since the load is in parallel with the diode, the voltage drop
across RL is always the same as across VR1 and is VZ =
constant Zener voltage
The input voltage V must be greater than VZ.
Zener MUST be operated under load. If not, the zener is still
delivering power (more than usual) and may melt. Recall that
the zener can draw large currents all at the same voltage.

SSGMCE, Shegaon
Circuits
Lecture 10
Half Wave Rectifier

Rectification
• Conversion of ac to dc.
– Many devices (transistors) are unidirectional
current devices
– DC required for proper operation.

Half Wave Rectifier

SSGMCE, Shegaon
Circuits
Lecture 11
Full Wave Rectifier & Filters

Full Wave Rectifier

Bridge Rectifier

Filters
• We have now used diodes to produced a pulsed
dc signal.
• Most equipment requires “regulated” dc
– We must remove the “ripple”
– Ripple is departure of waveform from pure dc (flat,
constant voltage level)
• Frequency – so far we have seen pulsed dc at the same
frequency as the input (½ wave) or twice the line frequency
(full wave rectifier)
• Amplitude – a measure of the effectiveness of the filter

Ripple Factor
out)
V(average
out)
voltage
ripple
(
V
r rms

Low r indicates better filtering

Alternate Definition
• Defined also for current
– Iac = effective value of ac harmonic component
– Idc = average of dc component
2
dc
2
rms
ac
2
ac
2
dc
rms
I
I
I
so,
I
I
I




1
I
I
r
I
I
r
2
dc
rms
dc
ac









For ½-wave rectifier r = 1.21
For full-wave rectifier r = 0.48

High Pass (RC) Filter
2
2
2
C
2
C
f
2
1
R
X
R
Z 












2
2
i
i
C
f
2
1
R
V
Z
V
I













High Pass Filter
• I is the same through both R and C
2
i
o
2
2
i
o
RC
f
2
1
1
1
V
V
C
f
2
1
R
RV
RI
V























When f is small,
denominator is large and the
voltage ratio is small.
When f is large, denominator
is almost one

Typical Results
R = 0.1 MW C = 0.16 mF
Why is it called a high pass filter?

Half Power Point
• Note the point at which
– This will make (Vo/Vi )2 = ½
– Recall that one form of power is V2/R, so the
output power is half the input power at this
frequency.
2
1
V
V
i
o 

Low Pass (RC) Filter
Z
V
I i

C
I
IX
IZ
V C
C
o




2
2
2
C
2
C
1
R
X
R
Z 











Low Pass Filter
 
 2
i
o
2
i
o
2
2
i
o
C
R
1
1
V
V
1
C
R
V
V
C
1
R
C
V
C
I
V


















Low frequency means denominator is small and Vo / Vi  1
High frequency means denominator is large and Vo / Vi is small

Low Pass Results
Note the half power frequency again.

Half Wave Capacitive Filter
• Improving the ripple factor
– During forward bias half-cycle, capacitor is charging
– During the reverse bias half-cycle, the capacitor
discharges through the output resistor

Full Wave Capacitive Filter
• Even better ripple factor.

L-Section Filter
• The series inductor opposes changes in current
• The coil stores energy when the current is above average and
releases energy to the circuit when the current falls below average
 Coil chops off (chokes) the peaks of the ac pulses
 L-section delivers more steady current than the capacitive filter alone
 Used for cases of variable loads where good regulation is required
 Output voltage is less than the capacitive filter

P Filter
Combines the effects of a capacitive and L-section
filter. Regulation is poor when load varies, however.

Introduction and importance of the electrical project LECTURE_PPTS.ppt

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