Zener Diode and its Working Principle

Zener diode is a special case of p-n junction diode which works in reverse bias.

In our house, there is a voltage fluctuation problem. And zener diode used as a voltage regulator.

We use zener diode as a voltage regulator in reverse bias.

Now, we will understand the Zener Diode and its Working Principle.

So, let's study the Zener Diode and its Working Principle.

Zener diode is a special type of the p-n junction diode.

The p-n junction diode is formed when we joined $n$ type and $p$ type semiconductor.

But in the zener diode, the n-type and p-type semiconductor both are heavily doped with the impurity.

The p-type semiconductor is doped with the Trivalent element like Aluminium.

And the n-type semiconductor is doped with the pentavalent element.

Because of the heavily doped p-n junction diode, its depletion region is very small i.e $10^{-6}m$.

And the small depletion region causes a very high electric field of order $\sim 5\times 10^6$ $V/m$ inside the zener diode.

Under the forward bias the p-n junction diode allows the Maximum flow of current.

Once the P-N junction is in forward bias it means that forward voltages are applied.

The width of the depletion region present at the junction decreases due to this forward bias.

As, reducing the width reduces impedance and the established path allows so maximum currents to flow.

And in reverse bias, it does not allow the flow of current because it behaves as an open circuit.

But in case of the zener diode, a very small amount of reverse current flow.

And again on increasing the voltage the current flowing in the opposite direction increases abruptly.

The abrupt increase in the value of the current because in reverse bias a large voltage pulls out the electron from the valence band.

And therefore, a large amount of current start flowing in the zener diode.

The graph of Current $(I)$ and Voltage $(V)$ of zener diode is shown as,

In reverse bias, the voltage at which the current abruptly increases is called a knee voltage.

This voltage is also called a breakdown voltage.

Because of the property of the flow of a large amount of current in the reverse bais.

when the reverse bias voltage is greater than zener voltage, a sharp breakdown takes place.

Therefore, Zener diode used as a voltage regulator.

And used in various devices to make our life easier.

Revision

Zener diode is a special type of the p-n junction diode.

The graph of Current $(I)$ and Voltage $(V)$ of zener diode is shown as,

The End