1. AD8684ARZ Substitution Conclusion The AD8684ARZ can serve as a partial substitute, but a rigorous assessment of supply voltage and output load conditions is mandatory, as it is not a direct drop-in replacement. The device is fully compatible in package (14-SOIC) and channel count (4 channels). Its J-FET input architecture offers superior input bias current (6 pA vs. 100 nA) and improved input offset voltage (350 µV vs. 1 mV), making it a better choice for precision sensing or sample-and-hold applications requiring high input impedance and low input current. The critical limitations are its significantly higher minimum operating voltage (9 V vs. 3 V), which precludes its use in single-supply, low-voltage systems (e.g., 5V or 3.3V), and its weaker output drive capability (12 mA vs. 30 mA), resulting in insufficient ability to drive heavy loads (such as low-impedance or large capacitive loads). Its bandwidth and slew rate are slightly lower, though this may not be impactful for general-purpose applications. Substitution should only be considered if the original circuit operates above 9V and drives a light output load.