SVC Department of Electronics

Zener Diode

A Zener Diode is a special kind of diode which permits current to flow in the forward direction as normal, but will also allow it to flow in the reverse direction when the voltage is above the breakdown voltage or ‘Zener’ voltage. Zener diodes are designed so that their breakdown voltage is much lower – for example just 2.4 Volts. Zener diodes are a special kind of diode which permits current to flow in the forward direction. Zener diodes will also allow current to flow in the reverse direction when the voltage is above a certain value. This breakdown voltage is known as the Zener voltage. In a standard diode, the Zener voltage is high, and the diode is permanently damaged if a reverse current above that value is allowed to pass through it. In the reverse bias direction, there is practically no reverse current flow until the breakdown voltage is reached. When this occurs, there is a sharp increase in reverse current. Varying amount of reverse current can pass through the diode without damaging it. The breakdown voltage or Zener voltage across the diode remains relatively constant.