Dynamic noise characteristics of tunneling magnetoresistance sensor under AC excitation

The tunnel magnetoresistance (TMR) sensor has the advantages of high sensitivity, easy miniaturization, and low power consumption, and it has the great potential to become a high-performance magnetic field measurement sensor. As the TMR magnetic sensor has complex noise characteristics, it is of great significance to explore the noise characteristics of TMR magnetic sensor for guiding its application. In this paper, the noise characteristics of the TMR magnetic sensor under different excitations are studied. It is found that the noise of TMR magnetic sensor under AC excitation is separated: some of the noise is dependent on the excitation and is moved to the excitation frequency synchronously with the output signal. The remaining part of the noise is independent of the excitation and remains in the low frequency band. Through the quantitative analysis of noise data, we find that the noise related to excitation accounts for about 70% of the total noise, while the noise unrelated to excitation accounts for about 30%. The results show that under AC excitation, 70% of the noise is synchronously modulated and 30% of the noise is separated from the signal, which provides an important guidance for the application of TMR magnetic sensor.