| 摘要 |
<p>A magnetic disk apparatus has a magnetic head (20) in contact with a flexible magnetic recording medium, for reading out data stored in the recording medium. The magnetic head is of the preceding-erase type. A converting circuit (25 to 27, 30) converts the output signal (SA) of the magnetic head (20) into digital read data (RD), and outputs it to the PLL circuit (32). The magnetic disk apparatus includes a preventing circuit for preventing the converting circuit from outputting to the PLL circuit the digital read data which is correspond read out data from the DC erased areas in the tracks of said magnetic recording medium (21). The preventing circuit comprises an AFG amplifier (24) for amplifying the signal read out of the magnetic head (20), a circuit for obtaining an envelope of the output signal of the AGC amplifier (24), and a circuit for preventing the converting circuit from outputting the read data when the signal level of the envelope is lower than a predetermined value.</p> |
