A Zener diode

A diode is usually regarded as the tool that supply power to one direction, but the Zener diodes are such that current can flow in the opposite direction if the applied voltage overshoot "voltage is broken" (breakdown voltage) or "Zener voltage".

Usual diode will not allow electric current to flow in the opposite if the reverse-biased (reverse-biased) below the breakdown voltage.
If the breakdown voltage exceeds the limit, regular diodes will be damaged because of excess electrical current that causes heat.
However, this process is reversible if done within limits.

In the case of rationing-forward (in the direction of the arrow), this diode will provide a voltage drop (voltage drop) of about 0.6 volts for a normal silicon diode.
The voltage drop depends on the type of diode used.

A Zener diode has properties similar to ordinary diode, except that the tool is deliberately made with a much reduced tengangan damaged, called Zener voltage.

A Zener diode has a pn junction which has a heavy doping, which allows electrons to penetrate (tunnel) from the valence band p-type material into the conduction band n-type material.

A zener diode is reverse-biased will exhibit a controlled breakdown and will pass an electric current to keep the voltage drop in order to remain on the zener voltage.

For example, a 3.2 Volt zener diode will show a voltage drop at 3.2 Volts if given the supply and forth.
However, because the current is not unlimited, so the zener diode is typically used to generate a reference voltage, or to stabilize the voltage for small flow applications.

Breakdown voltage can be controlled accurately in the doping process.
Tolerance of 0.05% could be achieved although the most usual tolerance is 5% and 10%.
This effect was discovered by an American physicist Clarence Melvin Zener.

Other mechanisms that produce the same effect is the avalanche effect, as in avalanche photodiodes.
Both types of diodes are actually formed through the same process and the effects actually occur in both types of these diodes.
In silicon diodes up to 5.6 volts, the zener effect is the main effect and this effect showed a negative temperature coefficient.
Above 5.6 volts, the avalanche effect becomes the main effect and also showed a positive temperature coefficient characteristics.

In the 5.6 volt zener diode, both effects occur together, and second temperature coefficients cancel each other.
Thus, diodes 5.6 volt the top choice in the temperature-sensitive applications.
The techniques of modern manufacturing has made it possible to create diodes which have a much lower voltage of 5.6 volts with a very small temperature coefficient.
But with the advent of high-voltage users, the temperature coefficient also appears with the speedy way. A diode for 75 Volt has a coefficient that is 10 times as much heat coefficient of a diode 12 Volt.

All the diodes on top, no matter whatever tengangan damage, usually sold called Zener diodes.

Usage

Zener diodes are usually used extensively in electronic circuits.
Its main function is to stabilize the voltage.
At the time are connected in parallel with a source voltage swings are mounted so that the dole and forth, a zener diode will act like a short circuit (short circuit) when the voltage reaches the diode voltage was faulty.
The result, the voltage will be limited up to a figure that has been known previously.

A zener diode is also used like this as a shunt voltage regulator (shunt connection is parallel, and voltage regulator circuit as a class that provides a fixed voltage source.