1. AD847JRZ-REEL Substitution Conclusion Direct substitution is not recommended. The AD847JRZ-REEL differs fundamentally from the original LT1122CS8 in key performance parameters, most notably in input architecture: the LT1122 employs J-FET inputs, offering extremely low input bias current (12 pA) and low input offset voltage (130 µV). It is suitable for applications requiring high input impedance and precision DC performance, such as high-impedance sensor amplification and integrator circuits. In contrast, the AD847 features a standard bipolar input, with an input bias current as high as 3.3 µA (nearly 300 times greater) and an offset voltage of 500 µV. In circuits demanding high input impedance or high DC accuracy, the AD847 would introduce significant errors and could even cause circuit malfunction. Although the AD847 outperforms the LT1122 in speed (slew rate 300 V/µs, bandwidth 50 MHz) and power consumption (5.3 mA), these advantages do not compensate for its fundamental shortcomings in input characteristics. Therefore, it is unsuitable for applications relying on the specific attributes of a J-FET input stage.