Skewed double differential pair circuit for offset cancellation

摘要

A differential system producing differential signals with offset cancellation utilizing a double differential input pair system is disclosed. It uses two parallel differential transistor pairs which are intentionally skewed. Nominally, the differential pairs are skewed in opposite direction from each, but with equal magnitude, so that the combination of the two differential pairs is nominally balanced. The current through each differential pair is then increased or decreased until any offset is sufficiently cancelled, using a selection means for providing an equi-potential value to first and second differential inputs in a calibration mode of the system and a comparison means for comparing first and second differential outputs in a calibration mode to determine the offset of the system.