| Summary: | 碩士 === 國立臺北科技大學 === 機電整合研究所 === 102 === The response of GMR output voltage’s component of the vector equal to the sensing axis is unipolar and has a magnetic hysteresis phenomenon. When driving by an AC magnetic field and detecting the odd harmonic signal synchronously, the response of the output voltage becomes bipolar and the magnetic hysteresis decreases. These results make the GMR become a sensor with a wider linear range. In the study we discuss about circuit design and fabrication of AC magnetic field driver and synchronous detection which can be applied on GMR magnetic. We use CIC TSMC 0.18 μm 1P6M CMOS processes to complete the circuit on chip. The circuit contains two parts: Excitation output circuit and sensing signal circuit. We use a 10 kHz square wave as an excitation field, and it can detect the offset between the GMR sensor Voltage-Magnetic curve affected by the outside magnetic. Finally, we can derive the DC output voltage linear to the magnetic field. Because the phase of the sensor output is easy to be affect by many factors, the circuit design contains a phase shifter to enhance the response of output voltage. In the future, we can integrate the driving circuit and the excitation coil into a single chip to complete the target of the “SOC” System on a chip.
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