Avalanche diode

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An avalanche diode is a diode (usually made from silicon, but can be made from another semiconductor) that is designed to break down and conduct at a specified reverse bias voltage.

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 in any such diode, but one usually dominates the other. Zener diodes are typically restricted to a few tens of volts maximum, but silicon avalanche diodes are available with breakdown voltages of over 4000 V.[1]

1 Uses
- 1.1 Protection
- 1.2 RF noise generation
2 See also
3 References

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Uses

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Protection

A common application is protecting 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. When used in this fashion they are often referred to as clamper diodes because they "clamp" the voltage to a predetermined maximum level. Avalanche diodes are normally specified for this role by their clamping voltage V_BR and the maximum size of transient they can absorb, specified by either energy (in joules) or I²t. Avalanche breakdown is not destructive, as long as the diode is not allowed to overheat.

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RF noise generation

An avalanche diode generates radio frequency noise, it is commonly used as a noise source in radio equipment. For instance it is often used as a source of RF for a Antenna analyzer bridge.

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