zener diode
Zener diodes are diodes that have the characteristics to channel electrical current flowing in the opposite direction if the applied voltage overshoot “voltage damaged” (breakdown voltage) or “Zener voltage”. This is different from ordinary diodes which only transmits electrical current to one direction.
Diodes normally will not allow electric current to flow in opposite if fed-back (reverse-biased) below the breakdown voltage. If you exceed the limit of breakdown voltage, normal diode 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 accordance with the direction of the arrow), this diode will provide voltage falls (voltage drop) of about 0.6 Volt ordinary silicon diode. Voltage drop depends on the type of diode used.
A Zener diode has characteristics similar to ordinary diode, except that this 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 fed through a broken behavior will exhibit a controlled and will pass an electric current to keep the voltage falls to keep the zener voltage. For example, a 3.2 volt zener diode will show a fall in the 3.2 Volt voltage if given the supply and forth. However, because the current is not constrained, so that 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 precisely in the process of doping. Tolerance of 0.05% can be achieved even though 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 the avalanche diode. Both types of diodes are actually formed through the same process and the effects actually occur in both types of these diodes. In a silicon diode, 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 a 5.6 volts zener diode, both these effects occur together and both temperature coefficients cancel each other. Thus, the diode is 5.6 volts to be the top choice of 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 briefly. A diode for 75 Volt has a coefficient of heat 10 times the coefficient of a diode 12 Volt.
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