To drive the gate of a switching MOSFET by a PWM signal whose duty changes over a wide range.

The device is structured mainly with a differentiating circuit 2 that differentiates an inputted PWM signal, a hold circuit 3 that holds the voltage of the differentiated rising waveforms to the input capacity of the gate to drive the gate of the MOSFET Q4, and a discharging circuit 4 that draws and discharges the voltage held to the input capacity of the gate based on falling differentiating waveforms when differentiated.