Seagate Technology Incorporated

David M Gray

William P Wood

Ray V Rigles

Terrence A McMahon

A head testing apparatus is provided for testing an output of a magnetic data recording head. The apparatus includes first and second tester input terminals for coupling to the head, first and second input stages and an AC-coupled differential amplifier. The first input stage has a first buffer input, which is coupled to the first tester input terminal, a first buffer output and a plurality of parallel-connected buffer amplifiers coupled between the first buffer input and the first buffer output. The second input stage has a second buffer input, which is coupled to the second tester input terminal, a second buffer output and a plurality of parallel-connected buffer amplifiers coupled between the second buffer input and the second buffer output. The AC-coupled differential amplifier has first and second amplefier inputs coupled to the first and second buffer outputs through first and second capacitors, respectively, and has a measurement output.

Transfer curve tester for testing magnetic recording heads

A balanced bi-directional current source is provided, which includes first and second current output terminals, a current control circuit, first and second amplifiers and first and second sense impedances. The current control circuit has a reference input, a feedback input, and a control output, which is based on the reference input and the feedback input. The first amplifier has a first amplifier input, which is coupled to the control output, and a first amplified output. The second amplifier has a second amplifier input, which is coupled to the control output, and a second amplified output, which is inverted relative to the first amplified output. The first sense impedance is coupled in series between the first amplified output and the first current output terminal and has a feedback output which is coupled to the feedback input. The second sense impedance is matched with the first impedance and is coupled in series between the second amplified output and the second current output terminal.

Balanced bi-directional current source

A head testing apparatus is provided for testing a magnetic data recording head. The apparatus includes a test volume adapted to receive the magnetic data recording head and a magnetic field source positioned to generate a magnetic field within the test volume. A Hall sensor is positioned relative to the test volume and has bias current input terminals, voltage output terminals, an operating temperature and an impedance between the bias current input terminals, which varies with the operating temperature. A bias current source is electrically coupled to the bias current input terminals and is adapted to provide a bias current, which is modulated based on the impedance of the Hall sensor.

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Bloomington, MN, United States of America

David M Gray