LEDs
form an inevitable part in the modern electronics as simple indicators
to optical communication devices. Light Emitting Diodes exploit the
property of the p-n junction to emit photons when it is forward biased.
LEDs are specially made diodes to emit light when a potential is applied
to its anode and cathode.
The
history of LED date backs to 1907 when Captain Henry Joseph observed
the property of electro-luminescence in Silicon Carbide. The first LED
was designed in 1962. It was developed by Holonyak worked at General
Electric (GE). It was a GaAsP device. The first commercial version of
LED came in the market during 1960s.
LED
technology industry became a boom during 1970s with the introduction of
Gallium Aluminium Arsenide (GaAlAs). These LEDs are high bright types
and are many times brighter than the old diffused types. Blue and White
LEDs was introduced in 1990 which uses Indium Gallium Nitride (InGaN) as
the semiconductor. White LED contains a blue chip with white inorganic
Phosphor. When blue light strikes the phosphor, it emits white light.
What makes LED ideal?
LEDs
are extensively used in electronic circuits because of its advantages
over bulbs. Some important features that make LED ideal in electronic
circuits are:
- LEDs are encapsulated in plastic or resin cases so that they can withstand mechanical shocks.
- Unlike bulbs, LEDs do not generate heat and power loss through heating is practically nil.
- LEDs require very low current and voltage typically 20 milliampere current and 1.8 volts. So these are ideal in battery operated circuits.
What is inside an LED?
Inside the casing of an LED, there are two terminal posts connected by a small chip made
of Gallium compound. This material exhibits the property of photon
emission when the p-n junction is forward biased. Different colours are
produced by dopping the base material with other substances.
Inside the Light Emitting Diode
