Head apparatus, hard disk apparatus and recording and playback apparatus

This invention relates to a head apparatus, a hard disk apparatus and a recording and playback apparatus, and more particularly to a head apparatus which includes a recording head for recording information onto a recording medium and a playback head for playing back the recorded information, and a hard disk apparatus and a recording and playback apparatus wherein the head apparatus is used to record and play back information onto and from a hard disk. A head apparatus which is tough against disturbing noise and superior in the S/N ratio and which can cope with an increase of the capacity of a recording medium is disclosed. A first playback amplifier for amplifying the playback signal of a MR head and a register circuit for setting the 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.