Amplifier circuits use an external power supply to generate an output signal that is larger than the replica of its input. One example are audio amplifiers that boost a speaker’s volume to cover a wider area. Voltage is the most commonly amplified type of input signal, but amplifiers can also increase current.
Most amplifiers perform linear amplification, but some are logarithmic in nature. The ideal amplifier has a high input resistance, a low output resistance, and minimal delay. The operational amplifier (op-amp) is a special type of differential amplifier with extremely high gain. Op-amps can be used with other components to perform mathematical operations, such as addition, subtraction, differentiation, and integration, in addition to amplification.
Factors to consider when purchasing an amplifier circuit include power consumption, input impedance, output impedance, frequency response, noise, and distortion.