To improve the precision of a signal waveform by selecting a count-up signal corresponding to a register optionally as a timing signal for output signal inversion so as to make a multichannel scale unchange and to obtain a minute duty ratio.

A register 50 that receives a count-up signal CU 1 and an output of a zero detector 16 detecting it that a count of a register R1 reaches zero provides an output of a signal α. On the other hand, a register 52 selects any of count-up signals CU2-CU4 as a timing signal that is used to invert an output signal P1 from an H level into an L level through a decode circuit 54 and a selector 56. In the case of setting by the register 52 to use the signal CU3, the decode circuit 54 gives a signal β to an AND circuit 62 to switch a selector 58 so as to select the signal CU 3. Thus, the count-up signal that is selected optionally is used for a timing signal to invert the output signal.