Get more accuracy from your DAC

摘要

With a DAC, you calibrate by initially determining the code-to-voltage error at one-third of the output range and again at two-thirds of the output range. The range between one-third full-scale and two-thirds full-scale avoids the output amplifier errors near the power-supply rails. The calibration of the offset and gain-error correction is a matter of simple algebra, where V{sub}(QUT)=a+bV{sub}(IN). In this formula, a is the offset error, and b is the gain error. You can accomplish these calibrations in the digital domain with the help of an ADC that is more accurate than a DAC's target specifications. This calibration technique is effective with offset and gain errors greater than 2 LSBs (least significant bits); however, the converter's quantization errors limit this approach.