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An '''amplifier''' is an electrical device which takes a small signal input and generates a large signal output that is reasonably faithful to the input.

An '''amplifier''' is an electrical device which takes a small signal input and generates a large signal output that is reasonably faithful to the input.

Typically, the input signal will be from a low voltage, high impedance source, and the amplifier output will be high voltage and low impedance (especially when being used in an audio processing setup).

Typically, the input signal will be from a low voltage, high impedance source, and the amplifier output will be high voltage and low impedance (especially when being used in an audio processing setup).  For example, the [[magnetic]] mechanism in a [[microphone]], [[electric guitar]] or [[record player]] produces a very low electric current and would be inaudible as a sound signal.  Instead the current must be fed through an amplifier before being passed to audio speakers.  Amplifiers of this kind invariably involve [[potentiometer]]s to adjust the volume (or 'gain') - the degree to which the signal, and hence the sound, is amplified.

Many specialized amplifiers are used for various tasks, for instance, taking the signal from the final [[compressor]] in the signal chain at a [[radio]] station control room and boosting it to be fed to the [[broadcast]]ing [[antenna]].  Such amplifiers have output impedances that are [[impedance matching|carefully tuned]] to the antenna's characteristics to ensure maximum power transfer.

Many specialized amplifiers are used for various tasks, for instance, taking the signal from the final [[compressor]] in the signal chain at a [[radio]] station control room and boosting it to be fed to the [[broadcast]]ing [[antenna]].  Such amplifiers have output impedances that are [[impedance matching|carefully tuned]] to the antenna's characteristics to ensure maximum power transfer.