HIGH-ACCURACY CIRCUITS FOR ON-CHIP CAPACITANCE RATIO TESTING OR SENSOR READOUT

Novel CMOS circuits are described for the on-chip measurement of capac itor ratios. They can provide a high-accuracy A/D interface for capaci tive sensors, or allow the precise calibration of switched-capacitor D ACs, amplifiers and other circuits utilizing ratioed capacitors. Vario us structures are proposed and the limitations of their accuracy are a nalyzed. Computer simulations illustrate the operation and verify the anticipated robustness and high accuracy of the system even in the pre sence of nonidealities.