A Field-Effect Transistor (FET) is a type of transistor that uses an electric field to control the flow of current between its source and drain terminals. It belongs to the family of transistors, which are semiconductor devices used to amplify or switch electronic signals and electrical power. FETs are widely used in various electronic applications due to their high input impedance, low power consumption, and ability to operate at high frequencies.
There are three main types of Field-Effect Transistors:
MOSFET (Metal-Oxide-Semiconductor FET): MOSFETs are the most common type of FET and come in two major variations: the enhancement-mode MOSFET and the depletion-mode MOSFET.
Enhancement-Mode MOSFET: This type of MOSFET is normally off, meaning that there is no current flowing between the source and drain terminals when no voltage is applied to the gate terminal. Applying a positive voltage to the gate terminal creates an electric field that attracts charge carriers, allowing current to flow between the source and drain terminals. Enhancement-mode MOSFETs are commonly used in digital integrated circuits.
Depletion-Mode MOSFET: This type of MOSFET is normally on, with a small current flowing between the source and drain terminals when no voltage is applied to the gate terminal. Applying a negative voltage to the gate terminal depletes the charge carriers in the channel and reduces the current flow. Depletion-mode MOSFETs are less common than enhancement-mode ones and are used in specialized applications.
JFET (Junction Field-Effect Transistor): JFETs have a simpler structure compared to MOSFETs and are divided into two types: N-channel and P-channel JFETs.
N-channel JFET: In this type, the channel between the source and drain terminals is made of an N-type semiconductor material. Applying a negative voltage to the gate terminal creates an electric field that narrows the channel and restricts the flow of current between the source and drain terminals.
P-channel JFET: In this type, the channel is made of a P-type semiconductor material. Applying a positive voltage to the gate terminal narrows the channel and reduces the current flow between the source and drain terminals.
IGFET (Insulated-Gate FET): This is a general term that encompasses both MOSFETs and JFETs, as they both rely on an insulated gate to control the flow of current through the channel.
FETs are widely used in various applications, including amplifiers, switches, voltage-controlled oscillators, voltage regulators, and more. They are crucial components in modern electronics due to their versatility and performance characteristics.