The operational amplifier is an electronic integrated circuit that contains a multi-stage amplifying circuit. Its input stage is a differential amplifier circuit, which has high input resistance and zero-drift suppression capability; the intermediate stage mainly performs voltage amplification and has a high voltage amplification factor. It is composed of a pole amplifying circuit; the output pole is connected to the load, and has the characteristics of strong load capacity and low output resistance. Operational amplifiers are used in a wide variety of applications. Widely used in: communication network, consumer electronics, multimedia, industrial automatic control, instrumentation, liquid crystal display, automotive electronics, wearable devices and the Internet of Things and many other fields.