Gatejännite

Gate voltage is the electrical potential applied to the gate terminal of a transistor to control the current that flows through the device. The gate acts as a gatekeeper for the conductive channel between source and drain, and its voltage modulates the channel’s conductivity. In metal-oxide-semiconductor and junction-type transistors, the gate voltage is the primary control input for switching and amplification.

In MOSFETs, the gate is insulated from the channel by a thin dielectric layer. Applying a gate-source voltage (Vgs) creates an electric field that modulates the carrier concentration in the channel. For an n-channel MOSFET, increasing Vgs above a threshold voltage (Vth) induces an inversion layer that conducts current; for a p-channel MOSFET, negative Vgs with respect to the source does the same in the opposite polarity. The gate current is typically extremely small, since the gate is insulated, and only leakage flows in steady state. The device’s current also depends on other voltages, such as the drain-source voltage (Vds) and the body effect, which can shift Vth when the source-body potential changes. Gate capacitance determines the dynamic response and is central to switching speed and power consumption.

In JFETs, the gate forms a reverse-biased p–n junction with the channel. The gate voltage widens the depletion region and reduces channel width, limiting current. When the gate voltage reaches a pinch-off level, the current is nearly extinguished.

Gate voltage is central to digital logic, analog amplification, and power electronics, where it is used to turn transistors on and off, modulate signals, and set operating points.