Efficacy Studies of a Novel Field Feedback Circuit for Giant Magnetoresistance Sensors

Abstract

Magnetic-feedback approach for improving the characteristic of a GMR sensor has been attempted in some research works. These works demonstrated an improvement in the linearity, hysteresis of the GMR characteristic and also facilitate measurement of negative fields. In this work, an improved field-feedback approach for GMR (FFG) sensors has been presented. It has been shown that the FFG improves the above characteristics of the sensor and also increases its measuring field range. An integrator circuit has been included in the FFG design. The integrator improves the dynamic response of the conventional feedback approach, by increasing overall system-damping. Moreover, it also facilities use of high loop-gain in the circuit which helps to reduce measurement error. The FFG, additionally, implements a dual-operating point technique, suitable for static fields. The output in the conventional feedback approach is largely dependent on an electromagnetic coil, present in the circuit. Dual-operating points, for biasing the GMR sensor, can be used to eliminate the effect of this parameter, completely. Extensive simulation results validate both these inclusions. It shows a reduction of error from 18 % to a negligible value, with dual-operating point technique, for static input fields. Subsequent experimental results, with a suitable prototype, further affirm the working and utility of the FFG.