Current bias, current sense for magneto-resistive preamplifier,

Abstract

A current bias, current sense magneto-resistive preamplifier for a hard disk drive and related methods preferably includes an MR sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance. A preamplifying circuit is preferably connected to the MR sensor for providing the current bias thereto and for amplifying a detected change in electrical resistance. The preamplifying circuit includes a sensor biasing circuit for providing the current bias to the MR sensor and an amplifying output circuit for providing an amplified output signal representative of the detected change in current bias to the MR sensor. The sensor biasing circuit preferably includes a current source, a first amplifying circuit connected to the MR sensor for sensing the change in electrical resistance therefrom, and a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source. The sensor biasing circuit also includes a transconductance amplifying circuit connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit for providing an output current proportional to the voltage difference at the first and second inputs thereof. The preamplifier further includes a capacitor connected to the preamplifying circuit for providing stability to at least a portion of the preamplifying circuit.