Patent ID: 6054901
Filing Date: 2000-04-25
Classification: G11B,H03F

Abstract:
A low-noise preamplifier comprising:a current source for providing a current to a magneto-resistive sensor;an input transistor having a first current electrode coupled to the current source, a second current electrode for coupling to the magneto-resistive sensor and a control electrode;a biasing circuit coupled between the first current electrode and the control electrode of the input transistor for controlling the average current passing through the input transistor so as to match the current provided by the current source; anda transimpedance amplifier having a low impedance input coupled to the first current electrode of the input transistor and an output providing a voltage output signal to an output terminal of the preamplifier, wherein the transimpedance amplifier comprises a gain stage having an input and an output coupled to the output terminal and a load resistor coupled between the input and the output of the gain stage, and wherein the gain stage comprises a voltage amplifier.