Abstract: Disclosed is a disk drive servo system including a "switched-capacitor" digital filter means adapted to attenuate resonant vibration and enhance system stability and position loop control.

Abstract: A servo system is disclosed for use with a motor such as the drive motor for the head wheel of a recording and reproducing apparatus, for example. The servo system utilizes a phase comparator to phase lock a feedback signal supplied by a motor tachometer and a reference signal to control the phase and speed of the drive motor. The reference signal is generated by a digital processor which is adapted to adjust the phase of the reference signal to a predetermined lead relative to a standard frequency source and also includes means for adding or subtracting incremental phase adjustments by comparing the phase of said tachometer signal with the phase of said standard frequency source and providing error signals in said incremental amounts for adjusting the resulting reference signal that is applied to the tachometer phase comparator.