A MOSFET-only, 10 b, 200 ksample/s A/D converter capable of 12 b untrimmed linearity

The linearity of a successive approximation (SA) A/D converter is typically limited by its passive network. Published converters based on capacitive arrays or resistive ladders are limited to around 10 b if no trimming or calibration is used. Although static measurements show that MOS transistors are capable of excellent matching, few MOSFET-only converters achieved more than 10 b accuracy without self-calibration. This A/D converter adopts the current division ladder network based on MOSFETs. Extensive measurements on the MOSFET ladders with different resolutions and geometry establish the achievable linearity.