The OPAx328 feature true rail-to-rail input operation, with supply voltages as low as ±1.1V (2.2V). The design of the OPAx328 amplifiers includes an internal charge-pump that powers the amplifier input stage with an internal supply rail at approximately 1.6V greater than the external supply (V_S+). This internal supply rail allows the single differential input pair to operate and remain very linear over a very-wide input common-mode range. A unique zero-crossover input topology eliminates the input offset transition region typical of many rail-to-rail, complementary-input-stage operational amplifiers. This topology allows the OPAx328 to provide excellent common-mode performance (CMRR > 120dB, typical) over the entire common-mode input range, which extends 100mV beyond both power-supply rails. When driving analog-to-digital converters (ADCs), the highly linear V_CM range of the OPAx328 provides maximum linearity and lowest distortion.