1. ADA4004-4ARZ-R7 Substitution Conclusion The ADA4004-4ARZ-R7 is not a direct drop-in replacement for the OPA4227UA/2K5G4 and should only be considered under very specific conditions after careful evaluation. The key limitations stem from differences in supply voltage range and output drive capability. Its operating supply range (10 V to 30 V) is both narrower and starts at a higher minimum voltage compared to the original part (5 V to 36 V). This makes it unsuitable for any system operating below 10 V, especially common ±5 V or single 5 V rails. Moreover, its output current (10 mA) is significantly lower than that of the original device (45 mA), which substantially reduces its ability to drive low-impedance loads. In applications requiring driving subsequent stages, long cables, or ADC inputs, this can lead to output voltage distortion or degraded accuracy. While the ADA4004 offers slightly better gain bandwidth (12 MHz) and slew rate (2.7 V/µs), and its input bias current (40 nA) and offset voltage (40 µV) may be acceptable for general-purpose use, these performance advantages do not compensate for the fundamental system-level risks imposed by the restricted supply range and limited output drive.