Definition
An electronic circuit that takes a small input signal and produces a larger output signal of the same shape, using an external power source to supply the added energy. The output is a stronger version of the input, not a different kind of signal.
Plain English
A circuit that makes a weak electrical signal stronger so it can be used or measured more easily.
Context Anchor
Seen in aircraft electrical and avionics systems, especially in radios, audio panels, intercoms, sensors, and control units that must strengthen small electrical signals.
Derivation
From the Latin amplificare, meaning 'to make larger.' A circuit is simply a closed loop through which electricity flows. So an amplifier circuit is literally a loop that makes a signal larger.
Why Pilots Care
Most cockpit equipment depends on amplifier circuits. A weak antenna signal, a quiet microphone, or a small sensor reading would be unusable without amplification. When a radio sounds faint or a gauge reads erratically, the amplifier stage is often involved.
Intuition Check
An amplifier circuit does not create the original signal or add new information to it. It uses power to make the existing signal strong enough for the next part of the system to use.
Example Sentence 1
The amplifier circuit in the audio panel boosts the microphone signal so the controller can hear the pilot clearly.
Example Sentence 2
During the preflight inspection the technician verified that the amplifier circuit in the intercom system was functioning before engine start.