There is disclosed a write compensator which suppresses bit shift caused by
distortion of a read signal waveform of a read head in a disk drive adopting a
perpendicular magnetic recording system. The write compensator executes write compensation
during recording data based on the known relationship between bit shift which is
beyond an allowable range and a pattern of a data bit string of a data signal.
A write amplifier converts the write-compensated data signal into an electrical
signal by using the write compensator so as to suppress the bit shift, and supplies
it to a write head.
