| 摘要 |
PURPOSE:To execute exactly positioning of a head even at the time of write by applying a head positioning servo based on servo information before writing, so that a sound recording/reproducing head and a servo-use head are not operated substantially at the same time. CONSTITUTION:One round of each data track which has been written on a magnetic disk 1 is divided into plural pieces, and a part called a gap is provided between respective sectors. A servo head 2 reads data from a data track DT on the magnetic disk 1, and its read data signal is amplified by amplifiers 9, 13, and thereafter, its envelope is fetched by envelope detecting circuits 10, 11. As for the fetched envelope, its difference is taken by a differential amplifier 11, and it becomes a position (displacement) signal. In order to extract a position signal before writing, and to supply it as true servo-information (position signal) to a servo-controlling circuit, a sample and hold circuit 17 is provided on an output side of the differential amplifier 11, and also a magnetic disk control device 18 serving as a control means is provided. |
