Threshold voltage

The threshold voltage, commonly abbreviated as V_th or V_GS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (V_GS) that is needed to create a conducting path between the source and drain terminals. It is an important scaling factor to maintain power efficiency.

When referring to a junction field-effect transistor (JFET), the threshold voltage is often called pinch-off voltage instead. This is somewhat confusing since pinch off applied to insulated-gate field-effect transistor (IGFET) refers to the channel pinching that leads to current saturation behaviour under high source–drain bias, even though the current is never off. Unlike pinch off, the term threshold voltage is unambiguous and refers to the same concept in any field-effect transistor.