A Field-Effect Transistor (FET) is a type of transistor that uses an electric field to control the conductivity of a channel in a semiconductor material. It operates based on the principle of modulating the voltage applied to a gate terminal, which in turn alters the conductivity between the source and drain terminals.
This allows FETs to act as amplifiers or switches in electronic circuits, offering high input impedance and low output impedance compared to other transistor types like BJTs.
The term “FET” refers to a category of transistors characterized by their method of operation involving an electric field (the “field-effect”) to control current flow.
This distinguishes them from Bipolar Junction Transistors (BJTs), which rely on the movement of charge carriers (electrons and holes) through a semiconductor material.
FETs work by applying a voltage to the gate terminal, which creates an electric field across a thin semiconductor layer (typically silicon).
This electric field controls the conductivity of the channel between the source and drain terminals.
Depending on the type of FET (such as MOSFETs or JFETs), the channel can be enhanced or depleted of charge carriers, thereby allowing current to flow or preventing it, respectively.
The name “FET” reflects the fundamental operating principle of these transistors: the control of current flow through an electric field.
Unlike BJTs, which control current via the injection of charge carriers, FETs utilize the field effect to achieve similar functionality with distinct performance characteristics.
This naming convention underscores the unique mechanism by which FETs operate compared to other transistor types.