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Q&A Opto-coupler, slow turn off

I changed value of resistor R318 from 10 kΩ to 1 kΩ, and that alone significantly improved off-time. From 200 μs to around 25 μs. That is much better. So I looked into datasheet again. I found t...

posted 5d ago by Chupacabras‭

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#1: Initial revision by user avatar Chupacabras‭ · 2024-10-12T18:38:14Z (5 days ago)
I changed value of resistor R318 from 10 kΩ to 1 kΩ, and that alone significantly improved off-time. From 200 μs to around 25 μs. That is much better.   

![Improved off-time](https://electrical.codidact.com/uploads/rrw4bpssyuzzatvzl7a8mm46iwhw)

So I looked into datasheet again. I found the answer on page 5, figure 8:  
![Switching time vs load resistance](https://electrical.codidact.com/uploads/8dwo8ynfxwedecygy1pbatniiyou)

Test circuit:  
![Test circuit](https://electrical.codidact.com/uploads/tkq4zbiqbq1t20lkm5p5avw1awvq)

It's surprising for me, that load resistance has such significant influence on the off-time.