Public address amplifiers are a device for amplifying the voltage or power of an input signal, consisting of an electron tube or a transistor, a power transformer and other electrical components. It is used in communication, broadcasting, radar, TV, automatic control and other devices. It can increase the amplitude or power of a signal and is an important part of signal processing in automation technology tools. The amplification function of the amplifier is realized by using input signals to control energy. The power consumption of amplification is provided by energy. For linear amplifiers, output is the repetition and enhancement of input signals.
For a nonlinear amplifier, the output has functional relation with the input signal. The public address amplifiers
are divided into mechanical amplifier, electromechanical amplifier, electronic amplifier, hydraulic amplifier and pneumatic amplifier according to the physical quantity of the signal processed. The most widely used one is the electronic amplifier. With the promotion of jet technology (jet element), the application of hydraulic or pneumatic amplifier is also increasing. The electronic public address amplifier is divided into the vacuum tube amplifier, the transistor amplifier, the solid amplifier and the magnetic amplifier according to the active components used. Among them, the transistor amplifier is the most widely used. In automatic instruments, transistor amplifiers are commonly used for voltage amplification and current amplification of signals, mainly in single-ended amplification and push-pull amplification. In addition, it is often used for impedance matching, isolation, current-voltage conversion, charge - voltage conversion (such as charge amplifier), and it has a certain function relationship between output and input using an amplifier.