Influence of local matching effects on the accuracy of a sequential A/D-converter

In sequential analog-digital converters there is a need for high precision copy components either in voltage or current techniques. In this work a switched current copier cell with high accuracy is shown. It uses a novel compensation technique which cancels offset due to mismatch. A sequential A/D-converter is presented using this cells as copyunits. The effects of local mismatch in the copycells on the accuracy of the converter is examined under different aspects concerning switch size, storage capacitors and mask-technology. The different aspects have been investigated by means of statistical simulation resulting in an improved circuit structure. The A/D-converter has been implemented in an 1.2 μm process