electrical presentation !

8/13/2019 Electrical Presentation !

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PN DIODES

Atif Imam

Avijit Jain

Avinash ReddyAviral Aggarwal

Ayush Asthana

Joshitha Reddy


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SEMICONDUCTOR

DIODETheory of p-n junction.p-n junction as diode.Ideal diode.

Volt-Current characteristics.Diode biasingDifferent types of Diodes.


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Theory of p-n junction

When a p-type semiconductor material is suitably joined

to n-type semiconductor the contact surface is called a

p-n junction.

++

Depletion region

P N


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p-n junction as diode Also called as semiconductor diode .

The left side material is a p-type semiconductor havingnegative acceptor ions and positevely charged holes.

The right side material is n-type semiconductor having

positive donor ions and free electrons .

Construction

NP

Symbol

Anode Cathode


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When forward biased, a diode acts as a conductor and

current flows

When reverse biased, a diode acts as an insulator and no current

flows.

Forward Biased Reverse Biased


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IDEAL DIODEWhen the diode is ON,

it acts like a short

circuit and current

flow

When the diode is OFF,current is zero, so it acts

like an open circuit


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Diode Biasing

D

RV

D

RV

Short circuit

I

Forward Biased

Reverse Biased

D

RV

D

RV

Open circuit

I = 0


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Types of Diodes

Light Emitting Diode (LED)

Avalanche Diode. Laser Diode.

Schottky Diode. Zener Diode. Photo Diode.

Varicap Diode or Varactor Diode. Rectifier Diode.


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ZENER DIODE

It was named after Clarence Zener, who discovered this electrical

property.

It Permits current in the forward direction as well as in the reverse

direction if the voltage is larger than the breakdown voltage or Zener

knee voltage or Zener voltage.

USES

Zener Diode Shunt Regulator.

Zener Diode as Peak Clipper.

Switching operation.
http://www.wikipedia.org/wiki/Clarence_Zenerhttp://www.wikipedia.org/wiki/Clarence_Zenerhttp://www.wikipedia.org/wiki/Clarence_Zener


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USES OF ZENER DIODE1. Zener Diode Shunt Regulator

2. Meter Protection

3. Zener Diode as Peak Clipper

4. Switching operation.


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Photo Diode A type of photo detector capable of converting light into either current or voltage.

Designed to operate in reverse bias.

n- region

p+ Active AreaInsulation

Depletion region

Back Metalization

n+ Back Diffusion

Front

Contact

Rear

Contact

Incident light

Absorbtion in the depletion

layer causes current to

flow across the

photodiode and if the

diode is reverse biased

considerable current flow

will be induced

USES :

Used in: CD Players. Smoke Detectors. Light sensors Various medical applications, such as detectors

for computer tomography and pulse oximeters.


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Tunnel Diode Esaki Diode) It was introduced by Leo Esaki in 1958.

Heavily-doped p-n junction

Impurity concentration is 1 part in 10^3 as compared

to 1 part in 10^8 in p-n junction diode Width of the depletion layer is very small

(about 100 A).

It is generally made up of Ge and GaAs.


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