Design of a Wide-Range and High-Precision Analog Front-End Circuit for Multi-Parameter Sensors

Abstract

This article presents a wide-range and high-precision analog front-end circuit for multi-parameter sensors that can handle sensor outputs of different types (R, C, V). A rail-to-rail baseline compensation method has been proposed, which further incorporates a fine offset elimination of 0.6 mV/step. Additionally, self-zeroing and correlated double-sampling techniques are integrated to reduce low-frequency noise and offset, prevent sensor signal saturation, and enhance the precision of the analog front-end circuit. By incorporating variable components in the sensor signal acquisition circuit and integrating them with the baseline compensation circuit, the applicability range of the sensor has been expanded (R: 7 Ω–1.7 MΩ, C: 50 fF–35 pF, V: 0.05–1.7 V). Test results show all interface circuits exhibit significant total conversion gains (C: 45 mV/fF, R: 14.5 mV/Ω, V: 144 V/V), achieving high precision. Meanwhile, a coefficient of determination (R2) greater than 0.998 indicates high conversion linearity of the circuit.

A Review of Optical Sensors in CMOS

“…The output signal of the APS is almost ready to be amplified, but not before subtracting the voltage V out,DC [V]. This process is known as correlated double sampling (CDS) [91][92][93] and measures the output signal twice. The first measure is performed in a known condition, while the second reading is performed in an unknown condition.…”