1. INA122U Substitution Conclusion Direct substitution requires careful evaluation of application conditions. The INA122U is fully compatible with the AD627ARZ in terms of supply voltage range, quiescent current, and package. Its higher bandwidth (120 kHz vs. 80 kHz) and slew rate (0.16 V/µs vs. 0.06 V/µs) are advantageous. The primary differences are as follows: First, input precision. The INA122U's input bias current (10 nA) is 5 times that of the AD627 (2 nA), and its input offset voltage (100 µV) is twice that of the AD627 (50 µV). When measuring weak signals or signals from high source impedances, this may introduce greater DC error and temperature drift. Second, output characteristics. The AD627 features rail-to-rail output, while the INA122U does not specify this capability. In applications using single-supply, low-voltage rails, or where maximum output dynamic range is critical, the INA122U's output swing may not approach the supply rails closely, leading to signal amplitude loss. Substitution may only be considered in applications where high input precision and wide output swing are not critical.