Zener Diode Working

A diode is an electrical component used to conduct electrical current in a single direction. A diode is known to have lower resistance in one direction and higher resistance in the other. 

A Zener diode is a special kind of electrical diode that can make the electrical current flow in the reverse direction. Thus, current flows from both the anode to cathode and vice versa in them due to heavy doping with impurities. 

The latter is not the case with normal diodes. Due to this functionality, these diodes find wide application as semiconductors in industries. 

The Zener diode working is based on the breaking of the circuit when the voltage reaches a point known as the Zener voltage. At this point, also known as knee point, the diode and the current flow reverse in what is called the Zener effect. That is why breakdown diode is another name for the Zener diode. 

For various Zener voltages, a variety of Zener diodes are present. Some of these diodes work for a variable amount of voltage.

Zener Diode Working Principle

The widening of the depletion layer resulting from the increase in the current flow forms the basis of the Zener diode working principle. 

Due to the continuous rise in voltage, the depletion layer keeps widening. Consequently, it increases the reverse current, eventually reaching its saturation point. At this point, the minority carriers of charge get enough energy to knock out the electrons still present in their external orbitals. 

This cycle keeps on repeating, and the cumulative effect of all the collisions taking place amongst the electrons leads to the conversion of the entire diode into a conductor. 

When the voltage reaches its saturation point, the circuit breaks down. However, the structuring of the Zener diode allows the current to flow in the opposite direction as well.

When working in the forward bias, the Zener diode acts as a normal diode. On the other hand, when placed in the reverse bias, the diode experiences the flow of small leakage current throughout the circuit. 

Eventually, the current starts to flow in the reverse direction when the reverse voltage achieves the diode’s predetermined level.  The current increases and reaches its highest value during this process, but a resistor controls it. Finally, the flow of current stabilises, and the diode starts to work over various voltages. 

Classification of Breakdown

We can classify the breakdowns that a Zener diode experiences into two categories, namely, Avalanche breakdown and Zener breakdown.

Avalanche Breakdown

This breakdown occurs in a diode when the voltage is very high. The process occurs when a high voltage is applied to the circuit, giving the electrons sufficient energy to accelerate at a higher velocity. 

These electrons moving at such high speeds collide with other electrons and provide them with the energy to move. This continuous collision of electrons produces a considerable amount of energy that increases the current in the diode. 

In normal conditions, such an increase in the electric current can lead to the destruction of the diode. However, the Zener diode’s design can withstand the increase in current.

Zener Breakdown

It is another type of breakdown seen in a Zener diode. 

When the voltage moves in the reverse direction and is close to reaching the Zener voltage, the electric field gets strong enough to pull the electrons from their outermost orbital. These free electrons increase the current flow, which subsequently increases the voltage leading to Zener breakdown.  

Conclusion

It is clear from the Zener diode working that it is a versatile semiconductor that allows current flow in both directions. Its functionality makes it find favourable usage for industrial purposes. 

The primary use of Zener diodes is as a voltage regulator. It is because of the diode’s design. Despite the increase in voltage, the circuit can break down and continue the current flow in the opposite direction.