Definition
An electronic amplifier in which the active device (transistor or vacuum tube) is biased so that it conducts current during only one half of each input signal cycle. Two devices are typically used in a push-pull arrangement, with each one handling one half of the waveform, so the full signal is reproduced at the output. Class-B operation is more efficient than Class-A but introduces some distortion at the point where the two halves meet.
Plain English
A type of amplifier where each of two transistors handles only half of the incoming signal, and together they rebuild the full signal at the output. This makes the amplifier run cooler and use less power than designs where the transistor is always on.
Context Anchor
Seen in aircraft radio, audio, intercom, and avionics maintenance discussions.
Derivation
The 'Class' system (A, B, AB, C) was developed by early radio engineers to categorize amplifiers by how much of the input cycle the active device conducts. 'B' simply marks the second category in that scheme — conducting for half the cycle (180 degrees) — sitting between Class-A (full cycle) and Class-C (less than half).
Why Pilots Care
Pilots don't tune Class-B amplifiers themselves, but understanding the term helps when reading about radio transmitter efficiency, audio panel design, or troubleshooting distortion in communication equipment.
Analogy
Think of two people pumping a swing by taking turns. One pushes during one half of the motion, and the other pushes during the other half. Together, they keep the full motion going.
Intuition Check
Do not read “Class-B” here as Class B airspace. In this term, “Class-B” is an electronics operating class for an amplifier circuit.
Example Sentence 1
The transmitter's final stage uses a Class-B amplifier to deliver high output power with reasonable efficiency.
Example Sentence 2
During the annual inspection the technician verified the Class-B output stage was free of crossover distortion.