A low-noise high-linear wide dynamic-range MTJ-based magnetic field sensor

Magnetic Tunnel Junction (MTJ) based sensors can function over a very wide range of magnetic fields, from pico tesla range to several milli-tesla. They have the potential to replace many currently used types of magnetic sensors in industrial and biomedical applications. This paper presents a readout channel using a double magneto-resistor (MR) bridge and a high-side current reference. The sensor system features offset cancellation and an intrinsic low-pass filter. The proposed magnetic sensor works with a linearity of better than 0.3% THD in a magnetic field range of +/- 0.5 mT and a bandwidth of 10 kHz. The measurement results show that the sensor input-referred noise power spectral density is 25.4 nVrms/root Hz at 100Hz equals 1.27 nT/root Hz.