Light Emitting Diode (LED)

by Monika Dadool 13-May-19

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LED stands for Light Emitting Diode. It is a pn junction diode which emit light after its activation through a suitable voltage. LEDs contain a transparent cover.


Operation occurs in LEDs
Conversion of electrical energy into light energy
A monochromatic light is emitted when it is accomplished in a forward based direction
Heavily doped in p-n junction i.e. high amount of holes and electrons


Principle and working of LEDs
It comprises of a semiconductor chip resided in the center containing two regions partitioned by a junction. Which further acts a barrier between the electrons flowing in p ad n regions. Battery is applied on forward bias and when some voltage is applied across leads, it create an electric field. The electrons in n regions get sufficient energy to easily move across p region junction. When ever an electron recombines with a positive charge, the energy transformation take place i.e potential energy get converted into an electromagnetic energy. When a negative and positive charge recombine, it emit a quantum amount of electromagnetic energy in the form of light.


Colors of LEDs
It comprises of gallium-based crystal containing materials such as phosphorous for generating a distinct color. It is mainly available in following colors:
a) Red
b) Green
c) Blue
d) White
e) Orange
f) Amber
g) Yellow


Want to know about = What is OLED?

Applications of LED
a) It is used in sensor and mobile applications including bar code readers, optical switches, encoders, and medical instrumentation, PDA's, laptops, general back-lighting, and digital cameras
b) LED signals
c) Transportation for passenger information queries
d) Indicators and illuminations
e) Automative fields for  enterier lightening, marker lights, tower, rail and vehicles
f) Lighting


Why LED's is preferred instead of traditional incandescent lamps:
a) It need less maintenance cost
b) It save energy
c) Enhance daylight visibility


Main reasons why LEDs is rapidly implemented in illumination applications
a) Decrease energy costs
b) Enhance attention capture
c) Less maintenance cost
d) Better visual appeal


Key characteristics to determine LEDs performance
a) Operating life
b) Voltage
c) Intensity
d) Color
e) White light
f) Eye safety labeling


Category of LEDs
a) Bargraph
b) Starburst
c) Dot matrix
d) Bargraph


Difference between visible LED's and invisible LED's

Visible LEDs
Invisible LEDs
Emit visible light
Emit infra red light which is known as invisible light
Used in display devices without photosensors
Used in photodiodes along with photosensors

Perk of LEDs
a) It consume less energy
b) Cheap
c) Less size
d) Light-weight
e) Long lifetime
f) Doesn't consist of toxic materials
g) These can emit light in different color
h) Quickly light-up


Dark side of LEDs
a) It only light with accurate electrical polarity
b) More attractive to insects
c) Expensive
d) Temperature dependence


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