COMPENSATING CIRCUIT FOR MAGNETIC DISK DEVICE

PURPOSE:To improve the stability and the quick-response of a follow-up control to a target track by putting a notch filter and a low pass filter into the loop of a compensating circuit. CONSTITUTION:A compensating circuit is composed of a read lag filter 3 to stabilize a control system, a notch filter 4 to compensate the resonance point of a mechanism system, a low pass filter 5 to remove a high frequency noise from a deviation signal showing the position dislocation of a magnetic head from a target track and a demodulating circuit 6 to generate the deviation signal from a servo pattern on a magnetic disk. To suppress the peak of a gain at the magnetic vibrating point of the lowest frequency, the notch filter 4 is putted in which a gain has a sharp trough opposite to this. Since the phase is delayed without fail at the low frequency side of the notch filter 4, the resonance frequency of the low pass filter 5 is made coincident with an antiresonant frequency applied to the frequency side higher than the resonance frequency of the lowest frequency of the mechanism system.