DISK APPARATUS AND SERVO-PATTERN WRITE SYSTEM

摘要

A disk apparatus comprising an MR (magneto-resistive) element as a reproduction element, and a disk including a servo-region and a data region. This apparatus is intended to prevent a reproduction error resulting from protuberances occurring on the disk, or a reproduction error of a so-called "thermal asperity", and particularly a read error of a start bit of a grey code by the thermal asperity occurring immediately before the grey code in the servo-region, and detects an erase region. In the construction of the present invention, a channel circuit includes a hysteresis comparator, which forms a servo-pattern so that the polarity of a reproduction signal of a start bit in the beginning of the grey code becomes opposite to the polarity of the signal generated by the MR element by the thermal asperity and alternately detects or reads signals of opposite polarities. As a result, error signals resulting from the thermal asperity are not read to prevent reproduction errors.