An amplifier is a device that can amplify the voltage or power of an input signal. It consists of an electron tube or transistor, a power transformer and other electrical components. Used in communication, broadcasting, radar, television, automatic control and other devices.An amplifier is a device that can amplify the voltage or power of an input signal. It consists of an electron tube or transistor, a power transformer and other electrical components. Used in communication, broadcasting, radar, television, automatic control and other devices.