/ˈmɒs ˌfɛt/
noun — "the switch that drives modern electronics."
MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a voltage-controlled transistor widely used in digital and analog circuits, including microprocessors, memory devices, power electronics, and RF amplifiers. MOSFETs are a subtype of field-effect transistors (FET) that use an insulated gate to control current flow between the source and drain, offering high input impedance, fast switching, and scalable performance.
Technically, MOSFET devices consist of a source, drain, and gate electrode separated by a thin oxide layer from a semiconductor channel. Applying a voltage to the gate induces an electric field that modulates the conductivity of the channel, allowing current to flow when turned on. MOSFETs exist in two polarities: n-channel (NMOS) and p-channel (PMOS), often combined in complementary configurations (CMOS) for logic gates and low-power circuits.
Key characteristics of MOSFET include:
- Voltage-controlled: gate voltage regulates channel current without significant gate current.
- High input impedance: minimal loading on preceding circuit stages.
- Fast switching: suitable for high-speed digital logic and RF applications.
- Scalable: can be miniaturized to nanometer-scale processes for integrated circuits.
- Power handling: available in low-voltage logic and high-voltage power versions.
In practical workflows, MOSFETs are used in digital logic circuits, switching power supplies, motor drivers, RF amplifiers, and analog signal processing. Engineers design CMOS logic gates, voltage regulators, and amplifier stages using MOSFETs to achieve high efficiency, minimal energy loss, and rapid response. Their controllable conduction properties make them essential for both low-power mobile devices and high-power industrial systems.
Conceptually, MOSFET is like an electronically controlled faucet: a small voltage at the gate fully regulates the flow of current from source to drain.
Intuition anchor: MOSFET powers virtually all modern electronics, combining speed, efficiency, and scalability in a single switch.