Low Power Circuit Interfaces for Strain Modulated Multiferroic Biomagnetic Sensors

The recording and analysis of biomagnetic fields have widespread applications in medical research and diagnostics. Wearable magnetic field sensors offer a noncontact and portable method for sensing biopotentials. This article presents a readout circuit in 180-nm CMOS for strain-modulated multiferroic vector magnetic field sensors. By utilizing a demodulator-first architecture, the circuit bandwidth and dynamic range requirements are greatly reduced allowing for a low power consumption of 5.9 mW. The circuit bandwidth is from 76 mHz to 2.2 kHz, allowing for measurement across the range of interest for biomagnetic signals. Utilizing a modulation noise cancellation technique, the noise performance of the sensor system is significantly improved, and the sensor modulation amplitude can be increased, resulting in improved sensor sensitivity. Measurements for the sensor-readout system demonstrate a 144 pT/<inline-formula> <tex-math notation="LaTeX">$\surd $ </tex-math></inline-formula>Hz magnetic noise floor at 1 kHz. The noise and power consumption are significantly lower than alternative magnetic sensor systems of similar volume.