MAGNETIC DISC DEVICE

PURPOSE:To perform alignment with high speed and accuracy, by synthesizing a low frequency component leading a phase of a position signal on a data plane with a high frequency component of a position signal on a servo plane in a magnetic disc device of sector servo system, and controlling head position. CONSTITUTION:In a data plane signal V1, the phase is led with a phase lead circuit T and outputted to points N' and Q' via resistors (R) 3 and 4. Servo plane position signals N and Q are given to differential amplifiers 4 and 13, and a synthetic signal viewed from the output of the amplifier 4 and 13 is given to an HPF consisting of (C)2R4 and C3R4 and the synthetic signal viewed from the output of the circuit T is given to an LPF consisting of C2R4 and C3R3. A synthetic signal OUT is outputted at a differential amplifier 10 to form the position control signal of the head. Thus, the phase of the signal OUT and that of the signal V1 are almost made equal, and the settling time for the compensation of offset caused at the switching of each data head can be reduced and the response time up to a prescribed alignment accuracy can be quickened.