Abstract: Reduced integration time within a lead-lag compensation circuit within a disk drive head positioner servo loop is reduced in the presence of a feed back position error signal which includes a bias force component. The compensation circuit including an integrating capacitor and a high value resistor through which the integrating capacitor is charged by the position error signal. Charging time of the integrating capacitor is reduced during track settling by a parallel resistance switchably connectable across the high value resistor for lowering the resistance thereof. A switch, such as a field effect transistor in series with the parallel resistance, connects the parallel resistance across the high value resistor in response to a switching signal.

Abstract: A control circuit for a stepper motor is disclosed. The stepper motor is driven by a chopper drive circuit. The frequency and the duty cycle of the stator or motor winding to which the chopper drive circuit has supplied the current is measured. The frequency and duty cycle measured are related to the back EMF induced in the driven stator. The back EMF is filtered and is used in a negative feedback manner and is supplied to the quadrature phase of the stepper motor to provide a damped step response.