A 101 dB 123-pArms Current Readout Circuit With Automatic Current Control for Multimodality Electrochemical Sensing

This paper presents a highly integrated wearable electrochemical sensor chip for sweat monitoring, incorporating both a current readout circuit and a programmable excitation waveform generator circuit. The chip is fabricated using a 0.11 μm standard CMOS process. The design utilizes a high-resolution and wide dynamic range current readout circuit for multimodality electrochemical sensing. A bidirectional current sensing potentiostat, based on a cascode current mirror, is presented. The circuit achieves bidirectional current sensing while isolating the sensing electrode from the subsequent circuitry, enhancing its versatility for various electrochemical measurement techniques. Additionally, the implementation of a current feedback loop, in conjunction with an automatic amplitude control method and a current-mode digital-to-analog converter, not only extends the dynamic range of the input current but also effectively eliminates the background currents. This design achieves 101 dB current dynamic range and 123 pA current resolution in the detection current range of ±15 μA with an R² linearity of 0.9999. It also attains a nonlinearity of 0.07%, ensuring minimal distortion. The current readout circuit consumes 12 μA of static current from a 1.5 V supply.