Väljatransistor

Väljatransistor, often abbreviated as FET, is a type of transistor that uses an electric field to control the conductivity of a semiconductor channel. This field is created by applying a voltage to a gate electrode. Unlike bipolar junction transistors (BJTs) which use current to control current, FETs use voltage control, making them highly desirable for many applications due to their high input impedance and lower power consumption.

The basic structure of a field-effect transistor consists of a semiconductor channel and three terminals: a gate, a drain, and a source. The gate controls the width or depth of the channel, thereby modulating the current flow between the drain and the source. There are two main types of FETs: JFETs (Junction Field-Effect Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

JFETs utilize a reverse-biased p-n junction to create the electric field that controls the channel. MOSFETs, on the other hand, use an insulated gate electrode separated from the channel by a thin layer of oxide. This insulation provides an even higher input impedance compared to JFETs. Both N-channel and P-channel versions exist for each type, differing in the type of semiconductor material used for the channel and the doping of the surrounding regions.

Field-effect transistors are fundamental components in modern electronics, widely employed in amplification, switching, and signal processing circuits. Their ability to operate with very little gate current makes them ideal for battery-powered devices and digital integrated circuits, such as microprocessors and memory chips.