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Saturday, March 10, 2007

Diode

A diode is a semiconductor device which allows current to flow through it in only one direction. Diodes are the most widely used devices in low- and high-speed electronic circuits and in rectifiers and power supplies. Other applications are in voltage regulators, detectors, and demodulators. There are some type of diode that can be used for different purpose.

Zener Diode
Zener diodes is specially built to operate in reverse breakdown. Zener diode operate in the reverse direction. Zener diode usually used for voltage stabilization.

Varactor Diodes
The varactor diode is an ordinary pn-diode that uses the voltage-dependent variable capacitance of the diode. The varactor diode is widely used as a voltage-dependent capacitor in electronically tuned radio receivers and in TV.

Tunnel Diodes
The tunnel diode is an ordinary pn-junction diode with very heavy doped n and p regions. Because the junction is very thin, a tunnel effect takes place. An electron can tunnel through the thin depletion layer from the conduction band of the n region directly into the valence band of the p region. Tunnel diodes create a negative differential resistance in the forward direction, due to the tunnel effect. Tunnel diodes are used as mixers, oscillators, amplifiers, and detectors. They operate at very high frequencies in the gigahertz bands.

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