A High-Resolution Planar Hall Effect Magnetometer for Ultra-Low Frequencies

Recent reports have demonstrated field resolutions of planar Hall effect magnetometers in the picotesla range. Here, we report a significant improvement in the field resolution of these sensors by decreasing their preamplifier white noise and the sensing element 1/f noise. We design, build, and test a miniature transformer-matched amplifier with a record noise level of 200 pV/√Hz and improve the f...