Patent ID: 6252735
Filing Date: 2001-06-26
Classification: G11B

Abstract:
A voltage-biasing, voltage-sensing differential preamplifier, comprising:a first subcircuit, comprising a voltage-sensing differential amplifier having a first input connected to a first terminal of an MR element and a second input connected to a second terminal of the MR element, said differential amplifier providing an amplified output signal of a voltage signal from the MR element; anda second subcircuit, connected across the first and second terminals of the MR element, comprising:a first feedback circuit, connected to a node between series resistors connected across the first and second terminals of the MR element, said first feedback circuit providing a first error signal controlling a bias current across the MR element to hold an average potential across the MR sensor at a predetermined potential, and wherein said first feedback circuit further comprises:an average-voltage amplifier B having a first input connected to the node between the series resistors connected across the first and second terminals of the MR element providing a measure of the average potential across the MR element;a second input connected to a predetermined first reference voltage, and an output terminal connected in a feedback loop to the node between the series resistors connected across the first and second terminals of the MR element; anda second feedback circuit connected across the first and second terminals of the MR element, said second feedback circuit providing a second error signal controlling the bias current applied to the MR element to hold a bias voltage across the MR sensor at a predetermined voltage level.