Calibration algorithm for current-output R-2R ladders

Abstract: The paper presents a new calibration algorithm for current output R-2R ladders. The R-2R ladders are popular because they are easy to realise, but the resistance tolerances limit their linearity properties. However, it is possible to achieve higher linearity with self-calibration techniques. A formerly published algorithm by Cutkosky is available for the so-called Cutkosky R-2R ladders. A similar algorithm can be applied to the current-output ladders, which are widely used as MDAC or DAC. In the paper the Cutkosky divider is shortly discussed, and then a new description is presented as basis of the calibration algorithm. The calibration algorithm is discussed in details, and the error budget is analysed. A simulator was also written to verify the theory.