Download Semiconductor device Semiconductor device

Birla Vishwakarma
Mahavidyalaya
1)SEMICONDUCTOR DEVICES
2)WORKING PRINCIPLE OF DIODE AND
SPECIAL DIODE
Branch: Electronics and Telecommunication
Branch code: 11, Semester: 03
Subject: Electronic Devices and Circuits
Subject code:2131006
NAME & ENROLMENT NO.
YOGESH IYER(140080111023)
NISHANT KUMAR(140080111032)
PARV JOSHI(140080111034)
KARNAV PANWALA(140080111033)
Semiconductor device
• Semiconductor device, electronic circuit component
made from a material that is neither a good conductor
nor a good insulator (hence semiconductor). Such
devices have found wide applications because of their
compactness, reliability, and low cost. As discrete
components, they have found use in power devices,
optical sensors, and light emitters, including solid-state
lasers.
• Semiconductor device have high conductivities, typically
from 104 to 106 Siemens per centimeter. The
conductivities of semiconductors are between these
extremes.
Semiconductor devices are as
follows:
• P-N Junction diode
• BJT
P – N Junction diode
• P-N Junction diodes are formed when a P
type semiconductor and N type
semiconductor are sandwiched together .
Types of Diodes
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Zener diode
Photo diode
LED
Tunnel diode
Schottky diode
Varicap
Transistor
• a semiconductor device, having three or more terminals attac
hed to electrode regions, in which current flowing between
two electrodes is controlled by a voltage or current applied to
one or more specified electrodes. The device is capable of a
mplification,etc, and has replaced the valve in most circuits si
nce it is much smaller, more robust, and works at a much low
er voltage.
V-I Characteristics
Semiconductor Devices
• Semiconductor devices don't follow ohms
law(V=IR)
• As the temperature increases the
conductivity of the device increases and
resistivity decreases.
• At high temp mobility of electron in these
devices is very high(µ=V/E)
Working principle of P-N
junction diode
Na
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n
Space Charge
Region
ionized
acceptors
ionized
donors
E-Field
+
h+ drift
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+
=
h+ diffusion
e- diffusion
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= e- drift
Types of Diodes and Their Uses
PN Junction
Diodes:
Are used to allow current to flow in one direction while
blocking current flow in the opposite direction. The pn
junction diode is the typical diode that has been used in the
previous circuits.
A
K
P
Schematic Symbol for a PN
Junction Diode
Zener Diodes:
n
Representative Structure for a
PN Junction Diode
Are specifically designed to operate under reverse breakdown
conditions. These diodes have a very accurate and specific
reverse breakdown voltage.
A
Schematic Symbol for a Zener
Diode
K
Special Diode
Varactor Diode
Varactor is a type of p-n junction diode that
operates in reverse bias. The capacitance of
the junction is controlled by the amount of
reverse bias.
Varactor diodes are also referred to as
varicaps or tuning diodes and they are
commonly used in communication systems.
A
C
d
Varactor diode symbol
..1 Basic Operation
The capacitance of a reverse-biased varactor
junction is found as:
(-1)
where, C = the total junction capacitance.
A = the plate area.
ε = the dielectric constant
(permittivity).
d = the width of the depletion region
(plate separation).
Reverse-biased varactor diode
acts as a variable capacitor.
Special Diode
Optical Diodes
There are two popular types of optoelectronic devices: light-emitting diode
(LED) and photodiode.
.4.1 The Light-Emitting Diode (LED)
LED is diode that emits light when biased in the forward direction of p-n
junction.
Anode
Cathode
(b)
(c)
The schematic symbol and construction features.
Special Diode
Application
The seven segment display is an example of LEDs use for display of decimal digits.
The 7-segment LED display.
Special Diode
The Photodiode
Photodiode is a p-n junction that can convert
light energy into electrical energy.
It operates in reverse bias voltage (VR), as
shown where Iλ is the reverse light current.
It has a small transparent window that allows
light to strike the p-n junction.
The resistance of a photodiode is calculated
by the formula as follows:
VR
RR 
I
Special Diode
Other Types of Diodes
The Schottky Diode
A Schottky diode symbol is shown The Schottky diode’s significant characteristic
is its fast switching speed. This is useful for high frequencies and digital
applications. It is not a typical diode in that it does not have a p-n junction.
Instead, it consists of a doped semiconductor (usually n-type) and metal bound
together, as shown in Fig.
Schottky diode symbol and basic internal construction of a Schottky
diode.
Special Diode
The Laser Diode
The laser diode (light amplification by stimulated emission of radiation)
produces a monochromatic (single color) light. Laser diodes in conjunction with
photodiodes are used to retrieve data from compact discs.
Basic laser diode construction and operation.
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