# What is Zener Diode & Its Application?

In this tutorial, we are going to learn about the Zener diode & its application.

## Zener Diode

A Zener diode is a special type of P-N junction diode and it can also work in reverse bias that makes it special.

In reverse bias, Zener diode works as a voltage regulator.

## V-I characteristics of Zener Diode

A voltage regulator circuit keeps the load voltage constant irrespective of changes in input voltage or load resistance.

## Zener Diode Application

Zener Diode as a Voltage Regulator

Voltage Regulator

• It is combination of elements designed to ensure that the output voltage remains constant.
• The resistor limits the total current flowing to the diode and the load. The load is connected across the diode.

Vo  = VZ

VS  – VR – VZ = 0

VR = VS – VZ

IR  = VS – VZ / RS

Kirchoff’s law :

IR  = IZ + IL   , IZ = IR – IL

## Ideal Approximation of Zener diode

Zener diode operating in breakdown region ideally act as a battery of value equal to breakdown voltage.

## Second Approximation of Zener diode

The total Voltage drop across the diode is equal to the breakdown voltage and voltage drop across zener resistance (RZ).

## Here below is the circuit for zener diode working

Regulating action of zener diode with varying input voltage:

When VI increasing: Vo  = VZ as long as

When VI decreasing: Vo  = VZ as long as

IZ  = I – IL

## Regulating action of zener diode with varying load resistance

1. When RL increases , If RL increases then IL decrease But I remains constant.

I  = IZ + IL

Since IL decrease then IZ increases

Therefore output voltage Vo = VZ as long as IZ < IZMAX

• When RL decreases, If RL decreases then IL increase But I remains constant.

Since IL increase then IZ decreases

Vo  = VZ as long as