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Ansari Mohammed Maviya 01
Saqib Ghatte 06
Burhanuddin Kachwala 32
Shubham Mayekar 18

1. Introduction to Diode
- Ansari Mohd. Maviya
P-N Junction and its formation
Formation of Depletion Layer
External Biasing of P-N Junction
V-I Characteristics of P-N Junction

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The cathode of a diode is represented by the silver
strip at the corner of the diode.
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P N
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• P side has high concentration of holes.
• N side has high concentration of electrons.
• Electrons from N sides diffuse over to P
• Holes from P diffuse over to N
This Process is known as Diffusion.

P N
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Depletion Region
• Positive immobile ions accumulate near junction on N side
• Negative immobile ions accumulate on P side

P N
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Current does not flows inside the circuit.

IF
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Light Emitting Diode (LED)
Zener Diode
2. Types of Diode
- Saqib Ghatte

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LED: Symbol:
• Light Emitting Diode (LED) is a special type of diode
emitting visible light when forward biased. These diodes
are not made from silicon or germanium because they
are heat producing materials and are not good in
emitting light radiations.

• A Zener Diode is a special type of properly doped crystal
diode which is designed to operate in the reverse
breakdown region.
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Zener Diode: Symbol:

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+ -
• Anode is connected to the positive terminal of battery.
• Cathode is connected to the negative terminal of battery.
• Anode is connected to the negative terminal of battery.
• Cathode is connected to the positive terminal of battery.

Zener Breakdown
Avalanche Breakdown
Comparison between Zener and
Avalanche Breakdown
3. Zener And Avalanche Breakdowns
&Their Comparisions
- Burhanuddin Kachwala

 There are two types of diodes
 Zener Breakdown
 Avalanche Breakdown

• When the P and N regions are heavily doped,direct rupture of
covalent bonds takes place because of the strong electric fields, at
the junction of PN diode. The new electron-hole paires so created
increase the reverse current in a reverse biased PN diode. The
increase in current takes place at a constant value of reverse bias
typically nelow 6 v for heavily doped diodes. As as result of heavy
doping of P and N regions, the depletion region width becomes
very small and for an applied voltage of 6 V or less, the field across
the depletion region becomes very high, of the order of 10 V/m,
making conditions suitable for Zener breakdown. For lightly doped
diodes, Zener breakdown voltage becomes high and breakdown is
then predominantly by Avalanche multiplication. Though Zener
breakdown occurs for lower breakdown voltage and Avalanche
breakdown occurs for higher breakdown voltage such diodes are
normally calls Zener diodes.
Zeners are commercially available with breakdown voltages
of 1.8 V to 200 V with specified tolerance from1% to 20 %

During reverse biased condition, in the case of less heavily doped PN
junction, Minority carries flowing across a junction acquire a kinetic energy which
increase with the increase in reverse voltage. At sufficiently high reverse voltage
(>5V) the K.E of minority carries become so large that they knock out electron from
the covalent bond of the S/C material. As a result of collision the liberated electron
in-turn liberated more electrons and the current becomes very large in the
junction leading to the breakdown of crystal in structure itself. This phenomena is
called the avalanche breakdown.
It occurs in lightly doped junction.
It produce wide depletion layer.
With increase in temperature avalanche
breakdown voltage increases.
Avalanche diode have
positive temperature coefficient .

ZENER BREAKDOWN AVALANCHE BREAKDOWN
1.This occurs at junctions which being
heavily doped have narrow depletion
layers
2. This breakdown voltage sets a
very strong electric field across
this narrow layer.
3. Here electric field is very strong
to rupture the covalent bonds
thereby generating electron hole pairs. So
even a small
increase in reverse voltage is
capable of producing large
number of current carriers. ie
why the junction has a very low
resistance. This leads to Zener
breakdown.
1. This occurs at junctions which
being lightly doped have wide
depletion layers.
2. Here electric field is not strong
enough to produce Zener
breakdown.
3. Her minority carriers collide
with semi conductor atoms in
the depletion region, which
breaks the covalent bonds and
electron-hole pairs are
generated. Newly generated
charge carriers are accelerated
by the electric field which
results in more collision and
generates avalanche of charge
carriers. This results in
avalanche breakdown.

Radio Demodulation
Power Conversion
Temperature Measurement
Voltage Protection
4. Applications of Diode
-r - Shubham Mayekar

It looks like this !!!!!!!!• The first use for the diode was the
demodulation of amplitude
modulated radio broadcasts.
• The history of this discovery is
treated in depth in the radio article.
• In summary, an AM signal consists
of alternating positive and negative
peaks of a radio carrier
wave, whose
amplitude or envelope is
proportional to the original audio
signal.
• The diode rectifies the AM radio
frequency signal, leaving only the
positive peaks of the carrier wave.
• The audio is then extracted from the
rectified carrier wave using a
simple filter and fed into an audio
amplifier or transducer , which
generates sound waves.

• Rectifiers are constructed from
diodes, where they are used to
convert alternating current
(AC) electricity into direct
current (DC).
• Automotive alternators are a
common example, where the
diode, which rectifies the AC
into DC, provides better
performance than the
commutator or
earlier, dynamo.
• Similarly, diodes are also used
in Cockcroft–Walton voltage
multipliers to convert AC into
higher DC voltages
It looks like this!!!!

• A diode can be used as a temperature
measuring device, since the forward
voltage drop across the diode depends on
temperature, as in a silicon band gap
temperature sensor.
• From the Shockley ideal diode equation
given above, it appears the voltage has a
positive temperature coefficient but
depends on doping concentration
and operating temperature .
• The temperature coefficient can be
negative as in typical thermostats or
positive for temperature sense diodes
down to about 20 Kelvin's.
• Typically, silicon diodes have approximately
−2 mV/˚C temperature coefficient at room
temperature.
It looks like this!!!!!!

• Diodes are frequently used to conduct
damaging high voltages away from
sensitive electronic devices.
• They are usually reverse-biased (non-
conducting) under normal circumstances.
When the voltage rises above the normal
range, the diodes become forward-biased
(conducting).
• For example, diodes are used in (stepper
motor and bridge) motor
controller and relay circuits to de-energize
coils rapidly without the damaging voltage
spikes that would otherwise occur.
• Many integrated circuits also incorporate
diodes on the connection pins to prevent
external voltages from damaging their
sensinsitive transistors.
• Specialized diodes are used to protect
from over-voltages at higher power
Its looks like this!!!!!!!!!

 Introduction to Diode
 P-N Junction and its formation
 Formation of Depletion Layer
 External Biasing of P-N Junction
 V-I Characteristics of P-N Junction
 Types of Diode
 Light Emitting Diode (LED)
 Zener Diode
Summary
 Breakdowns and Their
Comparison
 Zener Breakdown
 Avalanche Breakdown
 Comparison between both
 Applications of Diode
 Radio Demodulation
 Power Conversion
 Temperature Measurement
 Voltage Protection

 Books
 TechMax Pulications
 Vision Pulication
 VBD Pulications
 World Wide Web
 www.edurite.com
 www.wikipedia.org
 www.physicsforums.com
 www.diode.com
 www.thinkquest.org
References
 Presentations
 Analog Electronics Tutorial Series:
DIODES - Kristin Ackerson
 Basic Laws of Electric Circuits
 Diodes