An avalanche diode is a silicon diode that is designed to break down and conduct at a specified reverse bias voltage.
A common application is protecting avalanche diode electronic circuits against damaging high voltages. The avalanche diode is connected to the circuit so that it is reverse-biased. In other words, its cathode is positive with respect to its anode. In this configuration, the diode is non-conducting and does not interfere with the circuit. If the voltage increases beyond the design limit, the diode suffers avalanche breakdown, causing the harmful voltage to be conducted to earth.
Avalanche breakdown is due to impact ionization. Under a small reverse bias, the diode is almost non-conducting, although a very small current still flows. When the reverse electric field across the p-n junction is large enough, the energy of the few electrons flowing is enough to ionize atoms in the silicon. The ionization process is self-reinforcing, causing a rapid increase in current (theoretically taking only picoseconds to reach its peak). Avalanche breakdown is not destructive, as long as the diode is not allowed to overheat.
The Zener diode exhibits an apparently similar effect, but its operation is caused by a different mechanism, called Zener breakdown. Both effects are actually present diode avalanche in any such avalanche photo diode diode, but one may dominate the other.
See also
- Avalanche photodiode
- Zener diode
- Transil
- Varistor
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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