Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularities, a fully-differential potentiostat is designed with a wide output voltage swing compared to single-ended potentiostat. Two proposed potentiostats were implemented using TSMC 0.18-μm CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 500 pA to 10 uA. Besides, the dynamic range value can reach a value of 86 dB.
Keywords: amperometric sensor; dynamic range; fully differential; potentiostat; transimpedance.