Electronics
Course No: EEE 2211
Presented by :
Robin Sarker
Lecturer, EEE, KUET
Khulna University of Engineering & Technology (KUET)
Department of Electrical and Electronic Engineering(EEE)
1
Introduction
Reference books:
1.Electronic Devices & Circuit Theory- Robert Boylestad
2. Principles of Electronics- V.K. MEHTA
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
2
Electronics
Definition
The branch of engineering which deals with current
conduction through a vacuum or gas or semiconductor is
known as electronics.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
3
Introduction
Application of electronics
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
4
Introduction
Classification of Solids based on Energy Bands
Insulator
Robin Sarker
EEE,KUET
Conductor
Department of Electrical and Electronic Engineering(EEE)
Semicondutor
5
Introduction
Insulators. Insulators (e.g. wood, glass etc.) are those substances which do
not allow the passage of electric current through them. In terms of energy
band, the valence band is full while the conduction band is empty. Further,
the energy gap between valence and conduction bands is very large (15 eV)
as shown in Fig. 4.5. Therefore, a very high electric field is required to push
the
valence
electrons
to
the
conduction
band.
Conductors. Conductors (e.g. copper, aluminium) are those substances
which easily allow the passage of electric current through them. It is because
there are a large number of free electrons available in a conductor. In terms of
energy band, the valence and conduction bands overlap each other as shown
in Fig. 4.6. Due to this overlapping, a slight potential difference across a
conductor causes the free electrons to constitute electric current.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
6
Introduction
Semicondutors. Semiconductors (e.g. germanium, silicon etc.) are those
substances whose electrical conductivity lies in between conductors and
insulators. In terms of energy band, the valence band is almost filled and
conduction band is almost empty. Further, the energy gap between valence
and
conduction
bands
is
very
small
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
7
Introduction
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
8
Introduction
Intrinsic Materials
Without any impurities.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
9
Introduction
The process of adding impurities to a semiconductor is known as
doping.
Depending upon the type of impurity added, extrinsic semiconductors
are classified into:
(i) n-type semiconductor (ii) p-type semiconductor
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
10
Introduction
Extrinsic Materials
□ A semiconductor material that has
been subjected to the doping
process is called an extrinsic
material
□ n-Type Material
❖ The n-type is created by
introducing those impurity
elements that have five valence
electrons (pentavalent), such
as antimony, arsenic, and
phosphorus.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
11
Introduction
Extrinsic Materials
 Note that there is now an insufficient
number of electrons to complete the
covalent bonds of the newly formed
lattice. The resulting vacancy is called a
hole and is represented by a small
circle or positive sign due to the
absence of a negative charge. Since the
resulting vacancy will readily accept a
“free” electron:
The diffused impurities with three
valence electrons are called acceptor
atoms.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
12
Introduction
❖ Majority Carriers
− The majority carriers in n-type materials are
electrons.
− The majority carriers in p-type materials are holes.
❖ Minority Carriers
− The minority carriers in n-type materials are holes.
− The minority carriers in p-type materials are
electrons.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
13
Diode
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
14
Diode
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
15
pn-Junction
 One end of a silicon or germanium crystal can be dopedas
a p-type material and the other end as an n-type material.
 The result is a p-n junction
At the p-n junction, the excess conduction-band electrons on the n-type side
are attracted to the valence-band holes on the p-type side. The electrons in
the n-type material migrate across the junction to the p-type material
(electron flow).
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
16
Diode
Diodes
A diode is a two-terminal electronic component that conducts electricity primarily
in one direction
The ideal diode, therefore, is a short circuit for the region of conduction
The ideal diode, therefore, is an open circuit in the region of nonconduction.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
17
Diode
Diode Operating Conditions
□ A diode has three operating
conditions
❖ No bias
❖ Forward bias
❖ Reverse bias
The term bias refers to the application of an external voltage across
the two terminals of the device
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
18
Diode
Diode Operating Conditions- No Bias
□ No external voltage is applied: VD = 0 V
□ No current is flowing: ID = 0 A
□ Only a modest depletion region exists
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
19
Diode
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
20
Diode
Diode Operating Conditions- Reverse Bias
□ External voltage is applied across the p-n junction in the
opposite polarity of the p- and n-typematerials.
□ The reverse voltage causes the depletion region to widen.
□ The electrons in the n-type material are attracted toward the
positive terminal of the voltage source.
□ The holes in the p-type material are attracted toward the
negative terminal of the voltage source.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
21
Diode
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
22
Diode
Diode Operating Conditions- Forward Bias
□ External voltage is applied across the p-n junction in
the same polarity as the p- and n-type materials.
□ The forward voltage causes the depletion region to narrow
□ The electrons and holes are pushed toward the p-n junction
□ The electrons and holes have sufficient energy to crossthe
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
23
Diode
Actual Diode Characteristics
□ Note the regions for
no bias, reverse
bias, and forward
bias conditions.
□ Carefully note
the scale for
each of these
conditions.
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
24
Diode
Diode Equivalent Circuit
Ideal Diode:
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
25
Diode
Diode Equivalent Circuit
Simplified Model:
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
26
Diode
Diode Equivalent Circuit
Linear equivalent Circuit :
Robin Sarker
EEE,KUET
Department of Electrical and Electronic Engineering(EEE)
27
Determine the currents I1, I2, and ID2 for the network of Fig. 2.36
0.212 mA, 3.32 mA , 3.11 mA
Assignment
Department of Electrical and Electronic Engineering(EEE)
33