The amplifier uses power to control the electron flow in the electronic components within a certain range, thereby achieving signal amplification. In the amplifier circuit, the input signal enters through the input terminal, and after being amplified by internal transistors and other components, the amplified signal is output from the output terminal. The amplifier has different operating modes, including common emitter, common base, and common collector configurations. Each mode has its specific operating characteristics and application scenarios. For example, the common emitter configuration offers high amplification gain and low input impedance, making it suitable for most amplification purposes. The common base configuration has wideband characteristics and low input and output impedance, making it suitable for high-frequency applications. The common collector configuration provides high input impedance and low output impedance, making it ideal for buffer amplifiers and impedance matching applications.