Er. Swapnil V. KawareB.E.(Electronics), M.E.(Electronics & Tele.)

svkaware@yahoo.co.in

www.slideshare.net/svkaware1

“Light Emitting Diode”

CONTENTS:-

2

OBJECTIVES

PRE-REQUISITES/ENTRY LEVEL SKILLS

INTRODUCTION

WORKING

CHARACTERISTICS

APPLICATIONS

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OBJECTIVES:-

Able to identify terminals of LED.

Able to select appropriate materials for LED.

Able to know working of LED.

Able to plot characteristics of LED.

Able to state applications of LED

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After completing the session you will be…..

INTRODUCTION:-

A semiconductor device with two terminals.

The terminals are anode (+) and cathode (-).

It is works between voltage level 2V to 8V.

It emits light when activated .

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WORKING:-

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Fig:- (a)

Fig:- (c)

Fig:- (b)

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WORKING:-

Fig:- (d)Fig:- (e)

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When LED is forward biased, then the electrons from N region will combine with holes present in P region.

But due to heavily doped P region majority of free electrons will reside in conduction band.

Hence this free electrons goes into high energy state (i.e. at conduction band) & holes goes into lower energy state (i.e. at valence band).

But after the recombination, this electrons return back to the valence band i.e. at lower energy state.

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Hence by this way, when electrons come from higher state to lower energy state they generates excess amount of energy in the form of light or radiaton.

This process of LED is also known as ‘Electroluminescence’.

Hence on this principle LED’s generates light.

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CHARACTERISTICS:-

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MATERIALS USED:-

Gallium phosphide (GaP) for generating green light.

Gallium arsenide (GaAs) for generating red light.

Silicon carbide(SiC) for generating yellow light.

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LED’s are made up of…..

APPLICATIONS:-

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Sensor Applications Mobile Applications Security Applications Traffic Signals Illuminations Indicators

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SUMMARY:-

Identify terminals of LED.

Select appropriate materials for LED.

Know working of LED.

Plot characteristics of LED.

State applications of LED

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After completing the session it becomes easier to…..

Reference:- www.slideshare.net/svkaware

Have a nice day ahead!!!!

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