Amplifier

[1] An amplifier, electronic amplifier or (informally) amp is a 2-port electronic circuit or device increasing a signal (a time-varying voltage/current)'s magnitude to control larger external power sources via a power supply. Such signals are used to its input terminals, making a proportionally higher amplitude signal at its output. The amount of amplification given by an amplifier is measured by its gain: the output voltage ratio/current/power to input. An amplifier is defined as a circuit with a power gain greater than one.