1. BU7266SF-E2 Substitution Conclusion Not viable. Although the package is compatible and its quiescent current (700nA) is significantly lower than the original part (38μA), giving it a clear advantage in ultra-low-power applications, its key performance parameters are severely degraded and cannot meet the original design intent. The gain-bandwidth product (4 kHz vs. 130 kHz) and slew rate (0.0024V/µs vs. 0.048V/µs) are over an order of magnitude lower, resulting in extremely poor signal bandwidth and dynamic response, rendering it incapable of processing signals above very low frequencies. The input offset voltage (1 mV vs. 10 µV) is two orders of magnitude worse, severely degrading DC accuracy and making it unsuitable for precision amplification or sensor signal conditioning. Furthermore, its output drive current (4 mA vs. 30 mA) is significantly insufficient. This part is only suitable for extreme power-saving applications where only voltage presence detection is required, with no demand for speed or accuracy.