Executive Summary : | Graphene, the first experimentally realized two-dimensional material (2DM), has remarkable properties that make it suitable for various sensor applications, including Hall-effect magnetic sensors (HMS). The magnetic field sensitivity of graphene Hall-effect sensor (GHS) can be widely tuned by controlling the carrier type and density of the graphene channel using electrostatic doping in a gated GHS structure. A novel signal processing technique called ambipolar gate modulation can be harnessed to mitigate large sensor offset and low-frequency (1⁄f) flicker noise. The proposed sensor system consists of GHS and a CMOS ASIC. The proposed CMOS ASIC provides biasing voltage and controls common-mode bias and output voltages using a Current Bias DAC and a Common-mode Voltage Control circuit. The Hall sensitivity modulating control signal is generated using an on-chip Oscillator and a Gate Modulation Voltage Control circuit. The GHS output signal is amplified and demodulated using a low-noise Amplifier followed by a Demodulator & Filter circuit to obtain the final magnetic sensor output. Key advantages of the proposed system include the removal of large offset and flicker noise arising from both GHS and CMOS amplifier, improving the signal-to-noise ratio (SNR) by orders of magnitude. The ambipolar gate modulation technique is a low complexity signal processing scheme compared to the conventional spinning current technique used in semiconductor Hall sensors, leading to a low-power, low-cost ASIC. The simplified receiver architecture and nano-scale GHS array can lead to high resolution, high-SNR magnetic field imaging with potential applications in biological and industrial systems. |