Zenerdiode

A Zener diode is a type of diode designed to operate in reverse bias in the breakdown region, where it conducts in the reverse direction at a stable, well-defined voltage. It is commonly used as a voltage regulator, voltage reference, and protection element in electronic circuits. When a Zener diode is reverse biased and the voltage reaches its specified Zener voltage, the current through the diode increases without a large change in the voltage across it, effectively clamping the voltage.

The device is a heavily doped p-n junction, so it can enter breakdown at a relatively predictable voltage. The breakdown behavior arises from two related mechanisms: the Zener effect, which involves quantum tunneling at lower breakdown voltages (typically a few volts), and avalanche breakdown, which dominates at higher voltages. In practice, many Zener diodes feature a combination of both mechanisms, allowing stable regulation over a broad range of voltages and currents.

Common applications include precision shunt regulation in low-power supplies, voltage references in analog circuits, and transient voltage protection in some designs. Zener diodes are chosen for their relatively simple implementation, low cost, and ability to provide a stable reference voltage over moderate current variations. They are available in a wide range of nominal Zener voltages, and in various power ratings, from small signal types to power diodes capable of handling higher currents.

Key characteristics include a specified Zener voltage, a dynamic (or incremental) impedance, maximum current, and a temperature coefficient that describes how the voltage changes with temperature. Proper circuit design uses a series resistor to limit current and maintain operation within the diode’s specified range.