DIFFERENTIAL AMPLIFIER WITH ACCURATE INPUT OFFSET VOLTAGE

摘要

An amplifier (209) ( with accurate input offset voltage is described. In one design, the amplifier includes first and s (312, 314) receives a differential input signal and provides a first differential current signal. The second unbalanced differential pair (322, 324) receives a differential reference signal (Vref p, Vref n) and provides a second differential current signal, which is subtracted from the first differential current signal to obtain a differential output signal Ioutp, lout n) The second differential current signal tracks an error current in the first differential current signal so that the differential output signal is zero when the differential input signal is equal to a target input offset voltage for the amplifier. For each unbalanced differential pair, one transistor is M times the size of the other transistor, with M being selected to obtain the target input offset voltage.