Question

A Zener diode works on:

• A. Zero bias
• B. Reverse bias
• C. Forward bias
• D. Infinite bias

Answer 1

The correct option is B

Reverse bias

The explanation for the correct option:

In the case of option ($\mathrm{B}$)

1. When a $\mathrm{PN}$ junction diode is heavily doped with impurities, the depletion layer's breadth narrows due to the higher concentration of ions in the depletion layer than in a regularly doped $\mathrm{PN}$ junction diode.
2. The voltage decline across the depletion layer is relatively considerable due to the thinner depletion layer.
3. If a reverse voltage is provided to the Zener diode and then increased, the electrons within the depletion zone will come out and make the depletion region conductive after a specific applied voltage. This is referred to as a Zener breakdown.
4. When the Zenner diode is reverse biased, then the potential of the junction increases.

The explanation for incorrect options:

In the case of option ($\mathrm{A}$),

The voltage across the Zener diode remains virtually constant, but the current increases dramatically since the current path are conductive.

In the case of option ($\mathrm{C}$),

While the Zener diode behaves just like a conventional $\mathrm{PN}$ junction diode when connected in forwarding bias, its trait of a steep breakdown voltage in reverse bias is why we utilize it as a voltage regulator because it will only allow current to pass beyond a particular value.

In the case of option ($\mathrm{D}$),

The voltage point at which the voltage across the Zener diode allows the current to flow in reverse bias is called the Zener voltage. This voltage can range from less than one volt to a few hundred volts for normal Zener diodes. Therefore it does not work on the infinite bias.

Therefore, option $\mathrm{B}$ is the correct choice.