Abstract: A method and apparatus for re-initializing a GMR head after losing initialization is disclosed. The invention may use a voltage controlled waveform, which allows the current to vary with the resistance of the GMR head. Furthermore, according to a further aspect of the invention a stack of GMR heads may be reinitialized having the same orientation to preclude inversion of the reset magnetic fields on half of the heads. In addition, improvements in re-initializing GMR heads is provided by implementing wave shaping. The invention can also provide re-initialization of GMR heads at different points in the manufacturing process.

Abstract: A magnetoresistive transducer biasing technique that provides high common mode rejection ratio (CMRR) for a dual MR sensor head, while providing for short-circuit protection of the sensor elements within the head for short-circuits between the head and a disk.

Abstract: A circuit is disclosed for pre-amplifying signals from an MR sensor in a disk drive without producing output voltage transients as the MR head changes its operational mode. In one preferred embodiment, the circuit includes a bias current source, an input stage, and a voltage clamp across the inputs of the OTA of the input stage. The input stage remains active in all modes of the MR head to avoid transients generated by the thermal responses of the MR sensor. In a second embodiment, the circuit allows the current from a first current source to bypass the input stage and flows directly to the MR sensor in write or idle mode. The bias current remains generally constant in all modes, thus avoiding output transients. In the third embodiment, upon switching to read state, the MR sensor is biased with an additional current source to quickly heat up the sensor.

Abstract: Thermal transient signal detection/correction circuitry corrects for errors caused by actual thermal asperities and baseline wander in the analog signal from a magnetoresistive (MR) sensor, such as an MR read head in a magnetic recording disk drive. In a disk drive with an MR head the detection/correction circuitry is located between the MR head signal amplifier and the data readback channel so that the thermal transients are corrected in the analog data signal prior to processing of the analog data signal into digital data. A detection circuit receives the analog data signal from the MR head, low-pass filters the signal and generates a thermal asperity event signal if the filtered signal exceeds a predetermined threshold. A correction circuit also receives the analog data signal from the MR head and includes a high-pass filter whose pole frequency is controlled by the thermal asperity event signal from the detection circuit.