Provided are an input terminal (101) and an input reference terminal (102) for receiving an input signal, an output terminal (103) and an output reference terminal (104) for outputting a pulse signal after detection; a first detector circuit (106) that detects the input signal, and outputs an output signal to the output terminal and the output reference terminal; a normally-on type transistor (110) having a first terminal connected to the output terminal (103), a second terminal connected to the output reference terminal (104), and a control terminal; and a second detector circuit (108) that detects the input signal, and outputs a pulse signal of negative voltage to the control terminal of the transistor (110) using the output reference terminal (104) as a reference.
