Amplifier with capacitive feedback for driving a magneto-resistive head

摘要

A MR head amplifier of the present invention prevents a base potential of a transistor which supplies a current to a MR element from changing in a moment when the MR element changes from a write-state to a read-state. The MR head amplifier includes a loop amplifier that has a non-inverted input terminal connected to one end of a first transistor which supplies a current to a MR element and an inverted input terminal connected to one end of a second transistor which is supplied with a constant current through a constant current source. An output terminal of the loop amplifier is feedback to a base terminal of the first transistor via a first switch and one end of a capacitor whose other end is connected to a ground is connected to an output terminal of the first switch. The loop amplifier includes a second switch connected between the output terminal of the first switch and the base terminal of the first transistor, the second switch being closed during read-state and opened during write-state.