forwardbiased

Forward-biased describes a condition in semiconductor devices where a junction is biased with a voltage that lowers the potential barrier to carrier flow. In a p-n diode, forward bias occurs when the anode is at a higher potential than the cathode, reducing the depletion region and allowing charge carriers to cross the junction. The result is a rapid increase in current with increasing forward voltage, following the Shockley diode equation I = I_s (e^{V_f/(nV_t)} − 1). The forward voltage is not a fixed threshold; it depends on material, temperature, and device design. Silicon diodes typically require about 0.6–0.7 V to conduct appreciably, germanium diodes around 0.2–0.3 V, and Schottky diodes often around 0.15–0.45 V.

In transistors, forward biasing is a related concept applied to junctions. In a bipolar junction transistor, forward bias of the base-emitter junction (with the base more positive than the emitter) and reverse bias of the base-collector junction places the device in forward-active mode, enabling current amplification. In other device families, such as certain field-effect transistors, forward bias describes biasing directions that enable conduction through the channel or junctions, though terminology varies by device type.

Applications of forward bias include rectification in power supplies, signal demodulation, switching, and protection networks. Key considerations include device temperature, current handling, and the exponential nature of current increase with voltage, which defines performance in rectifiers, diodes, and transistor circuits.