Definition
A type of semiconductor device that uses an electric field to control the flow of current through a channel of semiconductor material. Current flows between two terminals (the source and the drain), and the amount of current is regulated by a voltage applied to a third terminal (the gate). Unlike a bipolar transistor, a field-effect transistor draws almost no current at the gate, giving it very high input impedance.
Plain English
A small electronic component that uses a small voltage to control a larger flow of electricity. The control side barely uses any current itself, so it is very efficient.
Context Anchor
Seen in aircraft electronics, avionics maintenance information, and descriptions of electronic control or amplifier circuits.
Derivation
Named for how it works: an electric 'field' (the invisible influence of a voltage) controls the current. 'Transistor' comes from 'transfer resistor' — a device that transfers a signal across a varying resistance.
Why Pilots Care
Field-effect transistors are the building blocks of modern avionics, radios, and digital displays. Knowing the term helps when reading equipment specifications or troubleshooting documentation.
Analogy
Think of it like a valve for electricity. Instead of turning the valve by hand, a small electrical signal changes how much current is allowed through.
Intuition Check
Do not read “field-effect” as meaning a magnetic field around the airplane or a radio signal in the air. Here it means an electric field inside the electronic part that controls current flow.
Example Sentence 1
The radio's input stage uses a field-effect transistor because it draws almost no current from the antenna signal.
Example Sentence 2
Modern aircraft radios rely on field-effect transistors to amplify weak signals without adding noise.