Light Emitting diode bulbs are fundamentally different from conventional incandescent lamps in terms of both structure and luminescence principles. Diodes are commonly used components in electronic circuits and are made of semiconductor PN junctions, with electrode leads and tube shells. Diodes have PN junction two electrodes, so called diodes. The diode has unidirectional conductivity.
There are many kinds of diodes, common detection tube, rectifier tube, regulator, switch tube, damping diode, light-emitting tube, photoelectric tube and so on. LEDs are usually made from semiconductor materials such as gallium arsenide and gallium phosphide, which glow when passing forward currents, and the color of the glow depends on the material used, emitting red, yellow, green, and infrared rays. Light emitting diodes are generally transparent plastic package, pin long for the positive, pin short for the negative. Some light-emitting diodes have three pins that emit two colors of light depending on the voltage of the pins.