Definition
A small solid-state electronic component made from semiconductor material that uses a small input current or voltage at one terminal to control a much larger current flowing between its other two terminals. It can act as either a switch (on/off) or an amplifier (making a weak signal stronger).
Plain English
A tiny electronic part that lets a small signal control a much bigger one. It can turn current on and off like a switch, or boost a weak signal into a stronger one.
Context Anchor
Seen in aircraft electrical and avionics maintenance, especially in circuit diagrams, radios, regulators, displays, sensors, and control units.
Derivation
From 'transfer' + 'resistor.' Coined in 1948 at Bell Labs because the device transfers a signal across a resistor. Knowing this hints at what it does: it moves and controls electrical signals rather than just blocking or passing them.
Why Pilots Care
Almost every electronic system in a modern aircraft depends on transistors. A technician troubleshooting avionics, charging systems, or instrument faults needs to recognize transistors on a circuit board and understand that they can fail in ways that disable the whole circuit.
Analogy
Think of a transistor like the small valve on a garden hose. A light touch on the valve handle controls a much stronger flow of water. The transistor does the same thing with electricity — a small signal controls a large one.
Intuition Check
Do not read transistor as just another kind of resistor. A resistor mainly limits current; a transistor uses one electrical signal to control another.
Example Sentence 1
The technician traced the radio fault to a failed transistor on the amplifier board.
Example Sentence 2
Modern aircraft use transistors to keep electrical systems lighter and more reliable than older designs.