Differential amplifier are designed to amplify the difference between two input signals. They can amplify a small difference between two signal levels and ignore any common level shared between them. This is particularly useful when the signal has traveled some distance and may have some added interference. If the signal travels over one of a pair of wires, the difference in potential between the wires can be assumed to be the signal. Differential amplifier chips or differential amps can reject any voltages common to both wires as noise caused by interference on both wires. For example, a differential amplifier chip can compensate for transmission losses over unshielded twisted pair (UTP) CAT-5 cables. A differential amplifier chip can also be used to control feedback. The second input to the amplifier chip is used to control the amplifier circuit. If necessary, a differential amp can be used to combine two signals. Most integrated amplifier circuits have differential amplifier input stages and can amplify the difference between two given input levels. For example, a differential amplifier can split a signal without loss, such as in cable splitter modules and multi-tuner cable set-top boxes.
Specifications for differential amplifier chips include -3 dB bandwidth, gain, minimum gain, supply voltage, supply current, offset voltage, slew rate, and harmonic distortion (second and third harmonics). Features for differential amplifier chips include number of leads (such as 8, 20, or 28 leads), standard packaging, and power-down features. As part of an integrated circuit chip an amplifier differential can be manufactured with standard packaging designs such as mini small outline package (MSOP).