Operational amplifiers (referred to as "operational amplifiers") are circuit units with high amplification factors. In practical circuits, feedback networks are usually combined to form a certain functional module. It is an amplifier with a special coupling circuit and feedback. The output signal can be the result of mathematical operations such as addition, subtraction, differentiation, and integration of the input signal. Due to its early application in analog computers to achieve mathematical operations, it was named "operational amplifier". Due to its early application in analog computers to achieve mathematical operations, it was named "operational amplifier". An operational amplifier is a circuit unit named from a functional perspective, which can be implemented by discrete devices or in semiconductor chips. With the development of semiconductor technology, most operational amplifiers exist in the form of single chips. There are various types of operational amplifiers that are widely used in the electronics industry. An operational amplifier is an electronic integrated circuit that contains a multi-stage amplification circuit. Its input stage is a differential amplification circuit, which has high input resistance and the ability to suppress zero drift; The intermediate stage mainly performs voltage amplification, with a high voltage amplification factor, and is generally composed of a common emitter amplification circuit; The output pole is connected to the load and has the characteristics of strong load carrying capacity and low output resistance. The application of operational amplifiers is very extensive. The operational amplifier has two input terminals a (inverted input terminal), b (in phase input terminal), and one output terminal o. Also known as the reverse input terminal, non reverse input terminal, and output terminal, respectively. When the voltage U - is applied between the A terminal and the common terminal (the common terminal is the point where the voltage is zero, which is equivalent to the reference node in the circuit), and its actual direction is higher from the A terminal than the common terminal, the output voltage U actually points from the common terminal to the O terminal, that is, the directions of the two are exactly opposite. When the input voltage U+is applied between the b terminal and the common terminal, the actual direction of U and U+is exactly the same relative to the common terminal. For the sake of distinction, terminals a and b are marked with "-" and "+" respectively, but do not mistake them for the positive and negative polarity of the voltage reference direction. The positive and negative polarity of the voltage should be separately marked or indicated by arrows