The direction of operation of an electrical or electronic device in which the device exhibits the larger resistance. A voltage applied in the reverse direction is a reverse bias and the current flowing is the reverse current.

A device such as a semiconductor diode exhibits an extremely high reverse resistance and can therefore be used as a rectifier or switch. Such a device exhibits a very small reverse saturation current below breakdown due to the movement of a few charge carriers across the p-n junction. The reverse recovery time of such a device, particularly a semiconductor diode, is the time interval between instantaneous switching from a forward bias to a reverse bias and the reverse current reaching the saturation value.