Threshold voltage

A nanowire MOSFET's current–voltage characteristic (left, using logarithmic y-axis) and a simulation of the electron density (right) forming a conductive inversion channel which connects at the ~0.45 V threshold voltage. Extremely little current flows below this voltage.

The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) 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.[1][2] 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 behavior 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.

  1. ^ "Junction Field Effect Transistor (JFET)" (PDF). ETEE3212 Lecture Notes. This is called the threshold, or pinch-off, voltage and occurs at vGS=VGS(OFF).
  2. ^ Sedra, Adel S.; Smith, Kenneth C. "5.11 THE JUNCTION FIELD-EFFECT TRANSISTOR (JFET)" (PDF). Microelectronic Circuits. For JFETs the threshold voltage is called the pinch-off voltage and is denoted VP.