1. B Y
A R U P C H A K R A B O R T Y
Super conductor & insulator
Semi conductor : intrinsic & extrinsic
Band theory of conduction
In mathematics, especially in geometry and group
theory, a lattice in R^n is a discrete subgroup of
R^n which spans the real vector space R^n .
Every lattice in R^n can be generated from a basis
for the vector space by forming all linear
combinations with integer coefficients.
A lattice may be viewed as a regular tiling of a space
by a primitive cell.
Lattices have many significant applications in pure
mathematics, particularly in connection to Lie
algebras, number theory and group theory.
4. Lattice Energy
The lattice energy of an ionic solid is a measure of
the strength of bonds in that ionic compound.
It is usually defined as the enthalpy of formation of
the ionic compound from gaseous ions and as such is
In the case of NaCl, the lattice energy is the energy
released by the reaction
Na+ (g) + Cl− (g) → NaCl (s) which would amount to
8. Superconductor & Insulator
Superconductivity is a phenomenon of exactly zero
electrical resistance and expulsion of magnetic fields
occurring in certain materials when cooled below a
characteristic critical temperature.
An electrical insulator is a material whose internal
electric charges do not flow freely, and which therefore
does not conduct an electric current, under the influence
of an electric field.
A perfect insulator does not exist, but some materials
such as glass, paper and Teflon, which have high
resistivity, are very good electrical insulators.
10. Intrinsic Semiconductor
An intrinsic semiconductor, also called an
undoped semiconductor or i-type
semiconductor, is a pure semiconductor without
any significant dopant species present.
The number of charge carriers is therefore
determined by the properties of the material itself
instead of the amount of impurities.
In intrinsic semiconductors the number of excited
electrons and the number of holes are equal: n = p.
11. Band Theory of conduction
12. Free & Bound Electron
• Free Electron : Electron that can move freely .
Electron without the coulombian attraction force of
Bound Electron : Electron that moves round the
Electron feeling the coulombian attraction force
with the nucleus .
15. Extrinsic Semiconductor
An extrinsic semiconductor is a semiconductor that
has been doped, that is, into which a doping agent has
been introduced, giving it different electrical properties
than the intrinsic (pure) semiconductor.
Doping involves adding dopant atoms to an intrinsic
semiconductor, which changes the electron and hole
carrier concentrations of the semiconductor at thermal
Dominant carrier concentrations in an extrinsic
semiconductor classify it as either an n-type or p-type
16. Semiconductor Doping
Semiconductor doping is the process that changes an
intrinsic semiconductor to an extrinsic semiconductor.
During doping, impurity atoms are introduced to an
Impurity atoms are atoms of a different element than the
atoms of the intrinsic semiconductor.
Impurity atoms act as either donors or acceptors to the
intrinsic semiconductor, changing the electron and hole
concentrations of the semiconductor.
Impurity atoms are classified as donor or acceptor atoms
based on the effect they have on the intrinsic
17. The two types of extrinsic semiconductor
18. N-type semiconductors
Extrinsic semiconductors with a larger electron
concentration than hole concentration are known as n-
The phrase 'n-type' comes from the negative charge of
In n-type semiconductors, electrons are the majority
carriers and holes are the minority carriers.
N-type semiconductors are created by doping an intrinsic
semiconductor with donor impurities.
In an n-type semiconductor, the Fermi energy level is
greater than that of the intrinsic semiconductor and lies
closer to the conduction band than the valence band.
19. P type Semiconductor
As opposed to n-type semiconductors, p-type
semiconductors have a larger hole concentration than
The phrase 'p-type' refers to the positive charge of the
In p-type semiconductors, holes are the majority carriers
and electrons are the minority carriers.
P-type semiconductors are created by doping an intrinsic
semiconductor with acceptor impurities.
P-type semiconductors have Fermi energy levels below
the intrinsic Fermi energy level. The Fermi energy level
lies closer to the valence band than the conduction band
in a p-type semiconductor.
22. Concept of Diode
What is a diode?: a diode is such a semi conductor
device which does not follow Ohm’s Law.
In electronics, a diode is a two-terminal electronic
component with an asymmetric transfer
characteristic, with low (ideally zero) resistance to
current flow in one direction, and high (ideally
infinite) resistance in the other.
A semiconductor diode, the most common type
today, is a crystalline piece of semiconductor
material with a p-n junction connected to two
A rectifier is an electrical device that converts alternating
current (AC), which periodically reverses direction, to direct
current (DC), which flows in only one direction. The process is
known as rectification.
Rectifiers have many uses, but are often found serving as
components of DC power supplies and high-voltage direct
current power transmission systems.
The simple process of rectification produces a type of DC
characterized by pulsating voltages and currents (although
Depending upon the type of end-use, this type of DC
current may then be further modified into the type of
relatively constant voltage DC characteristically
produced by such sources as batteries and solar cells.
27. Half Wave Rectification
In half wave rectification of a single-phase supply, either
the positive or negative half of the AC wave is passed,
while the other half is blocked. Because only one half of
the input waveform reaches the output, mean voltage
Half-wave rectification requires a single diode in a
single-phase supply, or three in a three-phase supply.
Rectifiers yield a unidirectional but pulsating direct
current; half-wave rectifiers produce far more ripple than
full-wave rectifiers, and much more filtering is needed to
eliminate harmonics of the AC frequency from the
29. Full Wave Rectification
A full-wave rectifier converts the whole of the input
waveform to one of constant polarity (positive or
negative) at its output.
Full-wave rectification converts both polarities of the
input waveform to DC (direct current), and yields a
higher mean output voltage.
Two diodes and a center tapped transformer, or four
diodes in a bridge configuration and any AC source
(including a transformer without center tap), are needed.
Single semiconductor diodes, double diodes with
common cathode or common anode, and four-diode
bridges, are manufactured as single components.
A transistor is a semiconductor device used to amplify
and switch electronic signals and electrical power.
It is composed of semiconductor material with at least
three terminals for connection to an external circuit .
A voltage or current applied to one pair of the transistor's
terminals changes the current through another pair of
Because the controlled (output) power can be higher
than the controlling (input) power, a transistor can
amplify a signal.
//Today, some transistors are packaged individually, but
many more are found embedded in integrated circuits.
39. About BJT
Bipolar transistors are so named because they conduct by
using both majority and minority carriers.
The bipolar junction transistor, the first type of transistor to
be mass-produced, is a combination of two junction diodes,
and is formed of either a thin layer of p-type semiconductor
sandwiched between two n-type semiconductors (an n-p-n
transistor), or a thin layer of n-type semiconductor
sandwiched between two p-type semiconductors (a p-n-p
This construction produces two p-n junctions: a base–
emitter junction and a base–collector junction, separated by
a thin region of semiconductor known as the base region
(two junction diodes wired together without sharing an
intervening semiconducting region will not make a