PS2501A-1-A Substitution Conclusion Based on electrical performance and core specifications, the PS2501A-1-A can serve as a fully functional replacement for the original part, PS2561AL2-1-V-F3-L-A. The critical parameters—including isolation voltage (5000 Vrms), current transfer ratio (50–400% @ 5 mA), output current (30 mA), saturation voltage (300 mV), and switching speed—are identical between the two devices. The primary differences lie in the package and a slight variation in forward voltage. The PS2501A-1-A uses a 4-DIP package instead of the original 4-SMD, requiring PCB layout redesign to accommodate through-hole mounting. This change also introduces minor differences in thermal management and board space requirements. The forward voltage difference (1.2 V vs. 1.17 V) is negligible and unlikely to affect drive circuit performance; therefore, no circuit adjustments are typically necessary. In summary, if the application allows for a through-hole package in place of surface-mount and the change in installation method is acceptable, the PS2501A-1-A is a direct and electrically equivalent substitute.