Analysis of Nonideal Effects on a Tomography-Based Switched-Capacitor Transducer

This paper presents a nonideal analysis of a fully-integrated switched-capacitor capacitive transducer for electrical capacitance tomography system. The investigation establishes different types of error source models as well as practical mismatch effects in the derivation of second-order analytical expressions. The analyses are conducted on the basis of heavy stray capacitances of 150 pF typically, in the context of a minimum detection capacitance ranging from 1 to 10 fF. The predicted results agree very well with the HSPICE simulation results using Level 49 BSIM3 models of AMS 0.6-mum CMOS process technology with a single 5-V supply. The conservative simulation results have shown that the capacitive transducer differential output displays a baseline dc offset of 0.083 mV at 25 degC, a change in baseline capacitance of 1 fF from 25 to 40 degC and an output temperature coefficient of 0.045 mV/degC from 25 to 100 degC at the measuring capacitance of 1 pF. Both the predicted and simulated results presented here are better than that of the reported works