Light Emitting Diode(LED) is semiconductor light source that emits light when current passes through it. . Electrons and holes releasing their energy in the form of photon(light). It work on the principle of electroluminuce.
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2-A LED array is a group of LED that display numbers ,letters and other symbols.
Application of LED:
1-The application of LED are in several places in instrument displays like; Calculator, Digital clock,etc.
2-A LED array is a group of LED that display numbers ,letters and other symbols.
3-The most common array of LED that it is 7 segment display.
Construction:
LED is three semiconductor layer substrate is sandwich between P-type and N-type semiconductor and active region. Active region is present in between P-type and N-type semiconductor layer. Light is emitted by active region.
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when LED is in forward biased so external energy strike on free electron of N-type semiconductor and it reach in excited state and holes are make in the place of free electron and electron release their energy in the firm if light.
some LED are colorful.The material used in LED are-
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Working:
LED work at the principle of electroluminuce. It is work only in forward biased. When it is in forward biased ,electron and holes are reach in the junction or depletion layer and they recombine with together then they release energy in form of light.
How to LED emits light:
when external voltage is applied to valence band so electron of valence band get excited and reach it in conduction band and stay here for short duration (10^-8 sec) the place of electron fill by the holes.Then electron get back in valence band with releasing energy(photon).The releasing energy are in the form of light.
image source:google
Symbol of LED;
image source;google
Characteristics of LED:
The amount of output light of LED is directly propositional to the forward current flowing through the LED. More forward current ,more grater output light. shown in graph-
Advantages of LED:
1-LED is fast operating device.
2-LED is available in various color.
3-LED has long life.
4-LED is easy to interface in other electric circuit.
Disadvantages of LED:
1-The efficiency of LED is very low which is about to 1.5 luminous/watt.
2-Need large power for operation as compared to normal P-N junction diode.
3-The characteristics are affected by temperature.
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