The Zener diode or avalanche diode is a normal diode made of semiconductor material, but operated in the reverse direction. In the reverse direction, the Zener diode has a sudden change in its resistance value at a certain voltage, the Zener voltage, which approaches zero at this voltage. The characteristic curve has an extremely steep characteristic in this range. The Zener voltage is relatively constant regardless of the current
. The Zener or avalanche effect is achieved by selective doping
ofthe semiconductor material and is at voltages
ofa few volts
up to several hundred volts.In the avalanche effect, charge carriers are released from the silicon
. These electrons are strongly accelerated by the electric fields that build up and release further electrons from the semiconductor like an avalanche. This is why the avalanche effect is also referred to as the avalanche effect.