1. Isolation Voltage: H11B3 (5300Vrms) is higher than H11B1M (4170Vrms). - If the system design depends on higher dielectric strength (e.g., reinforced insulation requirements or high-surge environments), the H11B1M may not meet the required safety margin, and insulation coordination should be reassessed. 2. Current Transfer Ratio (CTR): H11B1M (Min 500% @1mA) is significantly higher than H11B3 (Min 100% @1mA). - The H11B1M offers greater sensitivity to input current, providing stronger output drive under the same input conditions and potentially reducing the burden on the preceding stage. However, excessive CTR may increase sensitivity to the optocoupler’s dark current, requiring careful attention to stability design at elevated temperatures. 3. Output Stage Electrical Characteristics: - Output Voltage: H11B1M (30V) is superior to H11B3 (25V), offering better tolerance to load voltage transients. - Output Current: H11B1M is explicitly rated for 150mA, while H11B3 does not specify a maximum. - The H11B1M provides more margin in driving inductive loads or higher-voltage switching applications, but it is necessary to verify whether the original circuit operates near unspecified limits of the H11B3. 4. Input Drive Parameters: - Forward Voltage (Vf): H11B1M (1.2V) is slightly lower than H11B3 (1.35V). - Maximum Forward Current (If): H11B1M (80mA) is lower than H11B3 (100mA). - The H11B1M offers slightly higher LED driving efficiency, but its allowable transient current peak is lower. The original drive circuit should be checked to ensure it does not exceed 80mA. 5. Temperature Range: H11B3 supports -55°C, making it suitable for military or extreme environments; H11B1M is rated only for -40°C, which is the industrial standard. - The H11B1M is not suitable for applications involving startup or operation at ultralow temperatures.