The AD621ARZ-RL, as an instrumentation amplifier, cannot be directly substituted for the general-purpose amplifier OPA202IDR due to fundamental differences in amplifier type. The AD621 is designed specifically for precision measurement applications requiring differential inputs and high common-mode rejection ratio, whereas the OPA202 is a standard single-ended input general-purpose amplifier suitable for a wide range of amplification tasks. Key distinctions include the AD621’s higher slew rate (1.2 V/µs vs. 0.35 V/µs) and −3 dB bandwidth of 800 kHz, which enable faster response in high-speed signal processing. However, the AD621 exhibits a larger input offset voltage (75 µV vs. 20 µV), resulting in inferior DC accuracy. Its lower output current capability (18 mA vs. 35 mA) limits load-driving capacity, and its higher quiescent current (900 µA vs. 580 µA) increases overall system power consumption. Unless the original application specifically requires the differential input characteristics of an instrumentation amplifier, substitution is not advisable. Moreover, circuit redesign would be necessary to accommodate the different input architecture and performance profile.