The paper presents a new calibration algorithm for current-output R-2R ladders. The widely used R-2R ladders are easy to realise as an integrated circuit, but the resistance tolerances limit their linearity properties. However, it is possible to achieve higher linearity with self-calibration techniques. A formerly published calibration 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 of the inverse ladder is presented as a 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.
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