1. 4N33 Substitution Conclusion
The 4N33 can be used as a substitute for the H11G3, but critical parameter differences may necessitate design adjustments. The primary variances are: ① Current Transfer Ratio (CTR): The 4N33 has a minimum CTR of 500% @ 10mA, significantly higher than the H11G3's 200% @ 1mA. This gives the 4N33 stronger output drive capability at the same input current. However, due to differing test conditions, the gain matching at the actual operating point must be re-verified. ② Output Voltage: The 4N33's maximum output withstand voltage is 30V, lower than the H11G3's 55V. If the voltage at the output side of the original circuit exceeds 30V, breakdown may occur. ③ Saturation Voltage: The 4N33's Vce(sat) (1V) is slightly better than the H11G3's (1.2V), which is beneficial for reducing power dissipation. In summary, the 4N33 can substitute for the H11G3 if the circuit operating voltage is ≤30V and adjustments to the drive current due to CTR differences are acceptable.
2. 4N30 Substitution Conclusion
Substituting the H11G3 with the 4N30 requires caution, as key performance differences may impact system reliability. The core distinctions include: ① CTR: The 4N30 has a minimum CTR of only 100% @ 10mA, substantially lower than the H11G3's 200% @ 1mA. This may lead to insufficient output drive capability, necessitating a significant increase in input current or modification of circuit gain. ② Turn-Off Time: The 4N30's typical turn-off time of 40µs is superior to the H11G3's 100µs, which is advantageous for high-speed switching applications. However, this benefit may be offset by its CTR disadvantage. ③ Output Voltage: Similarly limited to 30V, the original design's voltage margin must be confirmed. Substitution may be viable if the application has low drive current requirements and the operating voltage is ≤30V. However, for most scenarios, a re-evaluation of circuit parameter matching is necessary.
Analysis ID: 9D7F-F123000
Based on part parameters and for reference only. Not to be used for procurement or production.
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