Patent ID: 6134060
Filing Date: 2000-10-17
Classification: G01R,G11B

Abstract:
A preamplifier for a hard disk drive, the preamplifier comprising:a magneto-resistive (MR) sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance;preamplifying means connected to a supply voltage and to said MR sensor for providing a current bias to said MR sensor and for amplifying a detected change in electrical resistance from said MR sensor, said preamplifying means including a current-source sensor biasing circuit for providing a desired biasing current to said MR sensor and an amplifying output circuit connected to said current-source sensor biasing circuit for providing an amplified output signal representative of the detected change in biasing current supplied to said MR sensor due to the change in electrical resistance, the current-source sensor biasing circuit including a current source for generating a source current, a first amplifying circuit connected to said MR sensor and to a supply voltage for sensing the change in electrical resistance from said MR sensor, a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source, and a transconductance amplifying circuit having first and second differential inputs respectively 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; andstabilizing means connected to said preamplifying means and to ground for stabilizing at least a portion of said preamplifying means.