When a switching amplifier transitions into a power-off state, a switch is turned off and a power supply controller forcibly discharges a capacitor and forcibly reduces a reference potential with respect to a second power supply voltage. Since a logic power supply voltage reduces by the same amount as the reference potential, the logic power supply voltage from a viewpoint of the reference potential is fixed. A constant current circuit reduces a constant current according to the reduction in the reference potential with respect to the second power supply voltage, and reduces a first electric current and a second electric current. Before the logic power supply voltage from the viewpoint of the reference potential reduces, the first electric current and the second electric current are reduced, and an operation of a pulse generating unit can be ended in a normal state.