High inductance coil embedded on on-chip magnetic sensor for biomagnetism measurements

Magnetic sensor chip for measuring biomagnetism is implemented in 0.18μm CMOS technology. The magnetic sensor chip consists of a small-sized high inductance coil sensor and an instrumentation amplifier (IA). The embedded high-inductance coil sensor contains suitable sensitivity and bandwidth for biomagnetic measurements, and is designed via electromagnetic field simulation. A low-gm operational transconductance amplifier is also implemented on the chip to reduce the transconductance value. The output signal sensitivity of the magnetic sensor chip is 3.25 fT/μV, and the output reference noise is 21.1 fT/ Hz. The instrumentation amplifier is designed to minimize the magnetic signal noise using current feedback and a band-pass filter with a bandwidth between 0.5 Hz and 5 kHz. The common-mode rejection ratio is measured at 117.5 dB by the Multi-Project Chip test. The proposed magnetic sensor chip is designed such that the input reference noise is maintained below 0.87 μV.