1. Semiconductor Devices
By
Md.Rabius Sani
Biplob Sarker
Fahmida Hossain
Bappy Das

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●Introduction
●Types of Semiconductor Devices
●Diode
●Forward & Reverse Bias
●Transistor
●Types of transistors
●Queries

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Introduction
●Semiconductor:
●Unit which consists lagely or wholly,of semiconductor
materials which can perform useful function in
electronic apparatus & solid state research.
●Ex:p-n jun diode,transistros,IC's and etc.

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Types of Semiconductors
●There are two types of Semiconductors
● 1)Intrisic Semiconductors
● 2)Extrinsic Semiconductors
●Intrinsic Semiconductors:Tetravalent
● Ex:Si,Ge etc
●Extrinsic Semiconductors:
Ex:p-type and n-type

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DIODE
●Diode is device with two
electrodes.
●A p-n juncion diode is a
two terminal device made
up of semiconductor
crystal.
●P-N junction diode
+ -
P-n junction diode ckt
symbol

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Forward Bias
●Resistance is very small
+ - mA
Depletion Layer
B
p n
P-n junction-Forward Bias

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Reverse Bias
●Resistance is very high
●Conduction is due to
thermal agitation.
Depletion Layer
B
+-
p n
MA
P-n junction-Reverse Bias

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Transistors
●Invented in 1948
●A transistor is a semiconductor device used to
amplify and switch electronic signal.
●Consist of two p-n junctions back to back
●Has three regions:
●1)Emitter
●2)Base
●3)Collector

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●Base is made up of P-
type
●Current conduction is
mainly due to holes
P-N-P Transistor
ppp pn
Ckt symbol of p-n-p transistor
E
B
C
p-n-p transistor

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N-P-N Transistor
●Base is made up of p-
type.
●Current conduction is
mainly due to electrons.
E C
B
n np
Ckt symbol of n-p-n transistor
n-p-n transistor

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Advantages
●Used in microcircuits.
●They're quite strong&sturdy.
●Usually,they've long life.
●Swithches turn on&off with the use of transistor.

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ANY QURIES?
●Can two diodes combined back to back as shown in
●fig to form a transistor?
P N N P

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THANK YOU