A 17.7µW CDS-CTIA for Wireless-powered Wearable Electrochemical Sweat Sensors

A capacitor transimpedance amplifier (CTIA) for wireless-powered wearable electrochemical sweat sensors is designed and tested. Correlative double sampling (CDS) technology is utilized to suppress offset voltage and noise. Dedicated low-power and low-voltage designs meet the requirements of wireless-powered wearable applications where the power supply is limited, and voltage is unstable. The proposed CDS-CTIA is fabricated in 0.18-µm complementary metal oxide semiconductor (CMOS) process, occupying an active area of 0.0285mm2. The measured low-frequency gain is 33.2MΩ/150.4dBΩ under a 1.8V supply voltage, with a total power consumption of 17.694µW (including 14.882µW static power and 2.812µW dynamic power). The input current ranges from -24nA to +19nA, and the input referred noise current is 7.76pArms in the 0.1-100 Hz frequency band. The proposed CDS-CTIA is capable of operating under a wide power supply ranging from 0.9V to 2.0V. In addition, its practicality is verified by measuring glucose concentration with an enzyme electrode.