DIGITAL-ANALOG CONVERTING CIRCUIT

PURPOSE:To perform D/A conversion with a simple constitution by obtaining a polarity signal and a signal having a pulse width corresponding to the absolute value of data from operation result data of a digital filter and integrating the polarity signal in the period of the pulse width to convert the digital signal to an analog signal. CONSTITUTION:A drum phase theta is obtained from an angular velocity omega of a drum motor 4 by an integrator 5, and the difference between this phase thetaand a reference phase thetaref is detected by an error detector 1 and is supplied to a D/A converting part 3 through an A/D converter 2. The D/A converting part 3 subjects a digitized error signal DELTAtheta to a prescribed operation processing and converts it to an analog signal to output a driving voltage em of the drum motor 4. This driving voltage em corresponds to the error signal DELTAtheta, and as the result, the drum motor 4 is stabilized in the state where it is rotated with the drum phase coinciding with the reference phase thetaref.