An amplifier includes a printed circuit board that includes an output terminal for outputting a electrical signal to an outside and a bias terminal for receiving a bias of the electrical signal from the outside, and an integrated circuit, a capacitor, an inductor, and a ferrite bead element mounted on the printed circuit board. The integrated circuit includes a driving circuit and an output end, and outputs the electrical signal generated by the driving circuit from the output end. The capacitor is connected between the output end and the output terminal A series circuit including the inductor and the ferrite bead element connected to each other in series, the inductor is connected to the output end, and the ferrite bead element is connected to the bias terminal.