A CMOS closed loop AMR sensor architecture

Abstract

A fully analog, closed loop, signal conditioning circuit is presented for the readout of Anisotropic MagnetoResistance magnetic sensors. The architecture is based on a fully differential design, consisting of an instrumentation amplifier with chopping to achieve low output noise, followed by a transconductor. The output current of the transconductor is directly fed back to the sensor, through a dedicated on-chip inductor for magnetic field offsetting purposes, closing this way a negative feedback loop. The proposed design has been implemented and simulated in TSMC 180nm 5 V CMOS process.