Diode-Based High Sensitive Capacitive Measurement

This paper presents a charge-transfer-based electronic read-out circuit dedicated to capacitive sensing. As compared to traditional approaches using controlled switches, it has a reduced circuit complexity and is not subject to charge injection offset errors. It uses a diode bridge and an integration stage to detect small charge variation in a differential capacitance structure with a resolution lower than a few fF on a 10 pF nominal capacitance value, in spite of the presence of important coupling paths to ground. The circuit is a good choice for many capacitive applications which require a low-cost, low-circuit complexity and a high sensitivity.