A frequency includes an input terminal, an output terminal, a transistor having a gate terminal which receives input of a signal including a first frequency from the input terminal, a source terminal and a drain terminal connected to the output terminal by a main line, an output matching circuit provided in the main line, the output matching circuit shutting off the first frequency while allowing an output frequency multiplied from the first frequency to pass therethrough, a branch line including a power supply terminal for connection to a power supply, the branch line branching off from a branch point in the main line, and a first diode provided in the branch line, the first diode having an anode connected to the power supply terminal and a cathode connected on the branch point side.