Integrating analog-to-digital converter with digital self-calibration

With dual-slope integrating analog-to-digital (A/D) converters, which are most frequently used for relatively low-speed conversion, the drift of the operational amplifier is a very critical factor in limiting their performance. The newly discovered digital self-calibration method, which completely eliminates the drift problem, is more readily adaptable to ratiometric conversion, where the input and the reference voltages are of the same polarity. Some of the advantages are: no necessity of manual adjustments, the use of inexpensive operational amplifiers instead of costly units with no performance degradation for the temperature range limited only by digital circuits, and the possibility of A/D converters operating on a single power supply. As is the case with the basic dual-slope converters, no precision components of high absolute or relative accuracy are required.