Reversebiased

Reversebiased is a term used in electronics to describe the condition of a p-n junction, most commonly a diode, when the applied voltage widens the depletion region and suppresses current flow. The more common spellings are “reverse bias” or “reverse-biased,” but variations without a hyphen or space can appear in some texts.

In a diode under reverse bias, the anode is at a lower potential than the cathode, preventing significant forward conduction. The current that does flow is primarily the reverse saturation current, a small leakage current due to minority carriers. This current increases with temperature. The depletion region expands as the reverse voltage increases, causing the device to present a high resistance and lower capacitance until breakdown occurs.

A key characteristic of reverse-biased diodes is their breakdown behavior. At a sufficiently high reverse voltage, breakdown mechanisms such as Zener or avalanche breakdown can occur, allowing substantial current to flow. Devices designed to operate in or near this region include Zener diodes used for voltage regulation, and avalanche photodiodes used for sensitive detection.

Applications of reverse bias include circuit protection against reverse currents, biasing and stabilization in detectors and sensors, and improving the performance of photodiodes by widening the depletion region for faster response and greater sensitivity. In transistor circuits, reverse biasing also applies to certain junctions to control operation, though excessive reverse voltage can damage devices.