Dual-slope 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 slow speed conversion, any drift in the operational amplifiers is a very critical factor in limiting their performance. A method has been proposed to eliminate the drift problem completely [1]. This short paper describes a similar but different approach to solve the problem. Some of the advantages are: no necessity for manual adjustments, the use of inexpensive amplifiers instead of costly units with no performance degradation for the temperature range limited only by digital circuits. The old method is more adaptable to ratiometric conversion, while the new method is more adaptable to normal dual-slope integrating A/D conversion with a reference voltage of opposite polarity to input signals. As is the case with the basic dual-slope converters, no precision components are required.