This paper reports a complimentary metal–oxide–semiconductor(CMOS) analog front-end chip for amperometric electrochemical sensors. The chip includes a digital configuration circuit, which can communicate with an external microcontroller by employing an I2 C interface bus, and thus is highly programmable. Digital correlative double samples technique and an incremental sigma–delta analog to digital converter(–? ADC) are employed to achieve a new proposed system architecture with double samples. The chip has been fabricated in a standard 0.18- m CMOS process with high-precision and high-linearity performance occupying an area of 1.3 1.9 mm2. Sample solutions with various phosphate concentrations have been detected with a step concentration of0.01 mg/L. The paper reports a complimentary metal-oxide-semiconductor (CMOS) analog front-end chip for amperometric electrochemical sensors. The chip includes a digital configuration circuit, which can communicate with an external microcontroller by employing an I2 C interface bus, and thus is highly The digital correlative double samples technique and an incremental sigma-delta analog to digital converter (-? ADC) are employed to achieve a new proposed system architecture with double samples. The chip has been fabricated in a standard 0.18- m CMOS process with high -precision and high-linearity performance occupying an area of ​​1.3 1.9 mm2. Sample solutions with various phosphate concentrations have been detected with a step concentration of 0.01 mg / L.