Analysis of nonideal effects on a tomography-based switched-capacitor transducer

Abstract

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- m 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 0.083mV at 25 C, a change in baseline capacitance of 1 fF from 25 to 40 C and an output temperature coefficient of 0.045 mV/ C from 25 to 100 C at the measuring capacitance of 1 pF. Both the predicted and simulated results presented here are better than that of the reported works.