1. LM258DG4 Substitution Conclusion Based on a comprehensive comparison, the LM258DG4 can generally serve as a substitute for the OP221GSZ-REEL in many common applications. However, its significantly worse input offset voltage (3mV vs. 250μV) poses a high substitution risk in critical applications demanding high DC precision or amplification of minute signals. The key differences and their impacts are as follows: On one hand, the LM258DG4 offers a wider supply voltage range (3-32V), lower quiescent current, and a higher gain-bandwidth product (1.1MHz). These characteristics may give it an advantage in single-supply, low-power, or applications requiring slightly higher dynamic response. On the other hand, its input offset voltage of up to 3mV is more than an order of magnitude worse than that of the OP221GSZ-REEL. This will directly introduce a non-negligible DC error into the amplification circuit, severely impacting amplification accuracy and system zero-point. Consequently, it is unsuitable for scenarios with stringent DC precision requirements, such as precision sensor signal conditioning or high-accuracy integrator circuits. Ultimately, the feasibility of this substitution depends entirely on the specific application's tolerance for DC error.