Magnetoresistive head amplifier
AssigneeSilicon Systems, Inc.
InventorAnatoly Aranovsky
Life of this patent
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Abstract
An amplifier for biasing and amplifying the signals produced by a magnetoresistive element is provided. The input stage of this circuit includes two transistors in a differential common base configuration having a low input impedance. Since the two transistors are coupled to separate identical current sources, balance between the currents through the two transistors is maintained. The currents are balanced without the use of a feedback loop. Additional input stages may be added to allow signals from additional magnetoresistive elements to be selected and amplified. By using a common mode switching configuration, switching transients are greatly reduced.
Claims15
A circuit for biasing a magnetoresistive element and amplifying signals produced by said magnetoresistive element, said circuit comprising:
- a first current source coupled to said magnetoresistive element and to a power supply;
- an input stage, comprising a plurality of transistors coupled in a first differential pair configuration wherein an emitter of a first transistor of said first differential pair of transistors is coupled to said magnetoresistive element, for amplifying current deviations resulting from variation of resistance of said magnetoresistive element;
- and
- a voltage source coupled to the bases of said first differential pair of transistors for providing a bias voltage;
- a second current source coupled to an emitter of a second transistor of said differential pair of transistors.
Apparatus for biasing a magnetoresistive sensor and amplifying signals produced by a magnetoresistive sensor when exposed to a changing magnetic field, said sensor having a steady-state resistance value, said apparatus comprising:
- current receiving means for receiving current from said magnetoresistive sensor, and for producing, in response thereto, signals representing a change in sensor resistance arising from changes in a magnetic field to which the sensor is exposed;
- amplifying means coupled to said current receiving means for amplifying said signals produced thereby, and having an output for transmitting said amplified signals therefrom, said amplifying means having a differential configuration with a first side of said differential configuration coupled to a second side of said differential configuration, wherein said magnetoresistive sensor is coupled between said amplifying means and a capacitor;
- biasing means for providing a bias signal to said amplifying means independent of said output.
A circuit for biasing a magnetoresistive element and amplifying signals produced by said magnetoresistive element, said circuit comprising:
- first amplifying means coupled to said magnetoresistive element;
- second amplifying means coupled to said first amplifying means in a differential amplifier configuration;
- a first current source for providing a first current through said first amplifying means;
- a second current source for providing a second current through said second amplifying means;
- and
- coupling means comprising a capacitor for coupling said signals to said second amplifying means.
A circuit for biasing a magnetoresistive element and amplifying signals produced by said magnetoresistive element, said circuit comprising:
- a first current source coupled to said magnetoresistive element and to a power supply;
- an input stage, comprising a plurality of transistors coupled in a first differential pair configuration wherein an emitter of a first transistor of said first differential pair of transistors is coupled to said magnetoresistive element, for amplifying current deviations resulting from variation of resistance of said magnetoresistive element;
- and
- a voltage source coupled to the bases of said first differential pair of transistors for providing a bias voltage;
- output means coupled to collectors of said first differential pair of transistors for transmitting output signals;
- a second current source coupled to an emitter of a second transistor of said differential pair of transistors.
Dependencies are inferred from the claim text.