In which biasing mode does a Zener diode operate effectively?

A Zener diode operates effectively in reverse bias mode. This mode allows the Zener diode to maintain a stable output voltage across its terminals when the voltage exceeds a certain threshold known as the Zener breakdown voltage. In this state, the Zener diode can conduct current without significant increases in voltage, making it invaluable for voltage regulation in circuits.

When reverse-biased, the diode enters its breakdown region, which is a controlled condition designed for Zener diodes. The ability to maintain a constant voltage across its terminals, regardless of variations in load current or input voltage, is what makes the Zener diode particularly useful in power supply circuits and voltage clamping applications.

In contrast, in forward bias, the Zener diode behaves like a standard diode, allowing current to flow in the forward direction, but this is not its designed operation mode for voltage regulation. A standard diode will have a forward voltage drop but will not provide the stable output that a Zener diode is intended to supply in reverse bias.