PURPOSE: To increase the number of gradation control by controlling an output voltage by using the pulse width shown by the analog time quantity which is obtd. by using the sample-held analog voltage for gradation and controlling the modulation of the analog pulse width.

CONSTITUTION: A sample-hold circuit 3 is channel-selected by a select signal and sample-holds the gradation data according to a timing pulse. The captured gradation data is taken into a switching circuit 4 according to the select signal. The gate by an AND gate circuit 6 is thereafter opened at the point of the time when all the data are captured. The captured data and a reference ramp voltage Vramp 14 are then compared and the gradation data (PWM control pulse) subjected respectively to the analog pulse width modulation are supplied to respective V/I conversion circuits 7. Namely, the gradation control of the display by using the pulse width indicated by the analog time quantity is analogically executed by sample-holding the gradation data. The number of the gradation control is increased in this way.