Impact of Adjustment of the Static Working Point on the 1/f Noise in a Negative Feedback GMI Magnetic Sensor

The resolution of giant magneto-impedance (GMI)based magnetic sensor is limited by its equivalent magnetic noise level. It presents a white noise and a low-frequency 1/f noise behavior. Previous works have showed that the white noise is mainly determined by the electronic conditioning noise, nevertheless, the 1/f noise's origin is not totally clear yet. To optimize the 1/f noise, in this paper, first, we develop an optimized negative feedback GMI sensor. It contains of a low-distortion oscillator, a high-performance amplitude detector, and a GMI sensing element with adjustable static working point. And then, the sensitivity and the 1/f noise level of the GMI sensor are studied when considering the electronic conditioning parameters and the static working point. The experiment results show that the adjustment of the static working point has a significant effect on the 1/f noise at low frequencies. The optimal 1/f noise is obtained by setting the static working point at the position where the GMI element possesses with the maximum intrinsic sensitivity. Finally, we achieve the GMI sensor noise performance of 20 pT/√Hz at white noise region and 100 pT/√Hz at 1 Hz.