Operational amplifier (referred to as "operational amplifier") is a kind of circuit unit with high magnification. In practical circuits, it usually forms a functional module together with the feedback network. It is an amplifier with special coupling circuit and feedback. Its output signal can be the result of mathematical operations, such as addition, subtraction, differentiation and integration of input signals. [ 1]?

Because of its early application in analog computers to realize mathematical operations, it was named "operational amplifier". Operational amplifier is a circuit unit named from the functional point of view, which can be realized by discrete devices or semiconductor chips. With the development of semiconductor technology, most operational amplifiers exist in monolithic form. There are many kinds of operational amplifiers, which are widely used in electronic industry.