| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the restriction on the circuit design such that a TA detecting circuit is arranged inside a preamplifier circuit in a disk drive of a perpendicular magnetic recording system using the preamplifier circuit including a differentiation circuit. SOLUTION: The preamplifier circuit 10 including the differentiation circuit 101 for differentiating a read signal read out from a read head and a read/write channel 11 including the TA detecting circuit 11 are disclosed in the disk drive utilizing the perpendicular magnetic recording method. The preamplifier circuit 10 is provided with a changeover circuit 102 for changing over an output of a read amplifier 100 and an output of the differentiation circuit 101, and it is constituted so that the output of the read amplifier 100 is transmitted to the read/write channel 11 by invalidating the output of the differentiation circuit at the time of TA detecting operation.
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