Head apparatus, hard disk apparatus and recording and playback apparatus

A head apparatus is disclosed which is tough against disturbing noise and superior in the S/N ratio and can cope with an increase of the capacity of a recording medium. A first playback amplifier for amplifying a playback signal of an MR head and a register circuit for setting a bias current to the MR head are formed as a COS IC. The COS IC is mounted on a suspension together with the MR head. A feeble playback signal outputted from the MR head is amplified by the first playback amplifier once and then transmitted to a mother IC over a pair of signal lines. The amplified playback signal is tough against disturbing noise during transmission.