1. LM2904ST Substitution Conclusion Direct substitution is not feasible and is only applicable to non-critical DC applications with extremely low requirements for precision, speed, and input error. The core difference between the LM2904ST and the OPA2137E lies in the input stage architecture: the LM2904ST features a standard bipolar input, with an input bias current (20 nA) that is 4000 times higher than the JFET input (5 pA) of the OPA2137E. This will introduce non-negligible DC offset error and temperature drift in high-impedance source circuits. Furthermore, its gain bandwidth product (700 kHz) and slew rate (0.6 V/µs) are significantly lower than those of the OPA2137E (1 MHz, 3.5 V/µs), resulting in a narrower bandwidth and severely inadequate capability for handling fast signals. Additionally, its output drive capability (30 mA) is only half that of the original part (60 mA). In applications requiring high input impedance, high precision, or moderate speed—such as sensor amplification, active filters, or audio pre-amplification—substitution will lead to significant performance degradation or even circuit failure.