A linear-approximation technique for digitally-calibrated pipelined A/D converters

Open-loop amplifiers enrich high-speed capability of pipelined analog-to-digital converters (ADC). Because both finite gain and circuit nonlinearity limit the accuracy of this approach, a linear-approximation calibration technique is proposed to compensate such non-ideal effects. Due to the nature of the two phase requirements, a double sampling technique is applied to achieve continuous-time on-line calibration without interrupting the normal data conversion. Pushing the complexity of calibration into the digital domain relaxes the stringent design requirements of analog circuits.