An amplifier is a device that increases the amplitude or power of a signal, and it is an important component for processing signals in automation technology tools. The amplification function of an amplifier is achieved by controlling the energy source with the input signal, and the power consumption required for amplification is provided by the energy source. For linear amplifiers, the output is the reproduction and enhancement of the input signal. For nonlinear amplifiers, the output is a certain function of the input signal. Amplifiers are divided into mechanical amplifiers, electromechanical amplifiers, electronic amplifiers, hydraulic amplifiers, and pneumatic amplifiers according to the physical quantities of the signals they process, among which electronic amplifiers are the most widely used. With the promotion of jet technology (see jet components), the application of hydraulic or pneumatic amplifiers is gradually increasing. Electronic amplifiers are divided into vacuum tube amplifiers, transistor amplifiers, solid-state amplifiers, and magnetic amplifiers according to the active devices used, among which transistor amplifiers are the most widely used. In automation instruments, transistor amplifiers are commonly used for signal voltage amplification and current amplification, mainly in the form of single ended amplification and push-pull amplification. In addition, it is commonly used for impedance matching, isolation, current voltage conversion, charge voltage conversion (such as charge amplifiers), and using amplifiers to achieve a certain functional relationship between output and input (such as operational amplifiers)