7.4.1 Rail-to-Rail Input

The OPAx320-Q1 feature true rail-to-rail input operation, with supply voltages as low as ±0.9 V (1.8 V). The design of the OPAx320-Q1 amplifiers include an internal charge-pump that powers the amplifier input stage with an internal supply rail at approximately 1.6 V above the external supply (V+). 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 OPAx320-Q1 to provide superior common-mode performance (CMRR > 110 dB, typical) over the entire common-mode input range, which extends 100 mV beyond both power-supply rails. When driving analog-to-digital converters (ADCs), the highly linear V_(CM) range of the OPAx320-Q1 provides maximum linearity and lowest distortion.