Signal reproducing circuit adopted for head utilizing magneto- resistive effect with control for reducing transient period between read and write states

摘要

A signal reproducing circuit includes: a magneto-resistive effect head having one end thereof coupled to a first power supply line, for reproducing data recorded on a magnetic recording medium in a read operation; a first constant current source coupled between another end of the head and a second power supply line, for supplying the head with a sense current in the read operation; first and second transistors having collectors thereof coupled to the first power supply line, and responsive to voltage signals obtained from both ends of the head; second and third constant current sources coupled between each emitter of the first and second transistors and the second power supply line, for supplying the first and second transistors with a predetermined constant current in the read operation; a capacitor connected between each emitter of the first and second transistors; and a control circuit responsive to a read/write control signal, for controlling respective ON/OFF timings of the first to third constant current sources. In a transition from a read state to a write state, the second and third constant current sources are first turned OFF and the first constant current source is then turned OFF. In a transition from a write state to a read state, the first constant current source is first turned ON and the second and third constant current sources are then turned ON. It is possible to reduce a transient idle period from a write state to a read state to thereby prevent an undesirable offset component from overlapping the reproduced signal, and to reduce a loss in the data capacity to a minimum.