A diode is a fundamental electronic component that allows the flow of electricity in one direction. A diode has low resistance to the flow of current in one direction and a very high resistance in the other. The diode most commonly used is the semiconductor diodes.
What is a Zener Diode?
Zener diode is a unique type of diode which allows the current to flow in one direction like a regular diode but it also permits it to flow in the opposite direction. It allows the flow in the opposite direction when the voltage is above a certain value known as Zener Voltage or Avalanche Point or Breakdown Voltage. A Zener diode consists of a highly doped, reverse biased (refer to an article on p-n junction diode) p-n junction diode while operating in the breakdown region.
Symbol of Zener Diode: The symbol of Zener diode is shown in below figure. Zener diode consists of two terminals: cathode and anode.
In Zener diode, electric current flows from both anode to cathode and cathode to anode. The symbol of Zener diode is similar to the normal p-n junction diode, but with bend edges on the vertical bar.
- A conventional reverse biased diode, when subjected to its breakdown voltage allows a significant amount of current. But when this reverse breakdown voltage is exceeded, the diode experiences an avalanche breakdown.
- Avalanche breakdown is a form of electric current conduction that allows very large current to pass through good insulators. This may permanently damage a conventional diode.
- A Zener diode exhibits the same properties except the Zener diode is designed to have a reduced breakdown voltage. In contrast to the conventional diode, a Zener diode exhibits a controlled breakdown.
- When we increase the voltage through Zener in reverse bias mode, first current increases uniformly with it but after it reaches the breakdown state, the current increases massively for a very small or negligible change in voltage. The change is sharper in Zener than the normal diode.
Advantages of Zener Diode:
- Power dissipation capacity is very high
- High accuracy
- Small size
- Low cost
Applications of Zener Diode:
- It is normally used as voltage reference
- Zener diodes are used in voltage stabilizers or shunt regulators
- Zener diodes are used in switching operations
- Zener diodes are used in clipping and clamping circuits
- Zener diodes are used in various protection circuits