PURPOSE: To directly drive a speaker with a switching emplifier, by aliminating noise caused due to a pulse width modulation signal through an inductive impedance inserted in series equivalently with the speaker.

CONSTITUTION: A system of low power consumption is constituted by using a C-MOS microprocessor 1 and a sound synthesis LSI2. When a voice is produced through the instruction of the microprocessor 1 only, the power supply is applied to the LSI2 and a switching amplifier 3 and others can be deenergized. That is, instruction is given from the processor 1 to the LSI2, allowing to produce a voice in response to the instruction. Further, the audio output system with pulse width modulation is adopted and conversion to an analog signal can be made without a D/A converter and an LPF, and no D/A converter, LPF and audio amplifier can be required at the outside of th LSI, and voice can be reproduced from a speaker 4 only with the connection of the switching amplifier 3 simply.