The OPA189, OPA2189, and OPA4189 (OPAx189) high-precision operational amplifiers are ultra-low noise, fast-settling, zero-drift devices that provide rail-to-rail output operation and feature a unique MUX-friendly architecture and controlled start-up system. These features and excellent ac performance, combined with only 0.4 µV of offset voltage and 0.005µV/°C of drift over temperature for the single-channel version, make the OPAx189 a great choice for precision instrumentation, signal measurement, and active filtering applications. Moreover, the MUX-friendly input architecture prevents inrush current when applying large input differential voltages, which improves settling performance in multichannel systems, all while providing robust ESD protection during shipment, handling, and assembly. All versions are specified from –40°C to +125°C.