Choose the correct statement about Zener diode:

We need to identify the correct statement about the behaviour of a Zener diode. A Zener diode is a specially designed p-n junction diode that is intended to operate in the reverse breakdown region and is manufactured with a precise breakdown voltage (called the Zener voltage, $$V_Z$$), typically by using heavily doped semiconductor material.

When a Zener diode is connected in forward bias (p-side connected to positive terminal), it behaves exactly like a normal p-n junction diode, conducting current once the applied voltage exceeds the threshold voltage (approximately 0.7 V for silicon), so there is nothing special about a Zener diode in forward bias.

In reverse bias, however, it blocks current flow until the reverse voltage reaches the Zener breakdown voltage $$V_Z$$. At this point, the diode enters breakdown and the voltage across it remains nearly constant at $$V_Z$$, even as the current through it varies over a wide range. This constant-voltage property makes it useful as a voltage regulator.

When used in a voltage regulator circuit, the Zener diode is connected in reverse bias across the load. If the input voltage fluctuates, the Zener diode adjusts the current through it to maintain a constant output voltage equal to $$V_Z$$ across the load, since in the breakdown region the voltage across the Zener diode remains essentially constant regardless of changes in current.

Therefore, the correct answer is Option (1): It works as a voltage regulator in reverse bias and behaves like a simple p-n junction diode in forward bias.