PN Junction

A PN junction is created when p-type semiconductor material (with excess holes) is brought into contact with n-type semiconductor material (with excess electrons). This junction forms a depletion region where charge carriers recombine, creating a built-in potential barrier. It exhibits rectifying properties, allowing current to flow easily in one direction (forward bias) while blocking it in the opposite direction (reverse bias). In clamping devices like TVS diodes, PN junctions are engineered to provide transient voltage suppression by avalanche breakdown at specific voltage thresholds.

The PN junction operates based on the diffusion of charge carriers across the junction and the formation of a depletion region. Under forward bias, the external voltage reduces the built-in potential, allowing majority carriers to flow across the junction. Under reverse bias, the potential barrier increases, preventing current flow until the breakdown voltage is reached. In TVS diodes, the junction is designed to undergo controlled avalanche breakdown at a predetermined voltage to shunt transient overvoltage surges to ground, protecting downstream components.