I spent 2 hours searching to know how does an optocoupler handles analog signals until I found your video ; answered pretty much all my questions. thanks !
Excellent video thanks. For anyone who may not know, if you remove the load resistor from the collector lead (pin 4) and positive source and put it between the emitter (pin 3) and ground (or the negative source) and measure between the emitter (pin 3) and ground, the output voltage will go positive as the input side goes positive.
@@minshijamusthafa3076 Think of the opto as being a resistor or a switch, which side you put the load on really doesn't matter, configure it to suit your needs. It's just a another series circuit element. Data sheets can't go into every possible configuration.
The Miller effect is one of the main limiter on the bandwidth. It you use another transistor as a cascode stage then you should be able to improve the frequency response considerably.
I have never seen a cascode on an optocoupler. Do you have direct experience or an example of a product that uses that? you can bootstrap a photo transistor if you have access to the base: www.epanorama.net/sff/Misc/Optical/Bootstrapping%20Phototransistors%20to%20Improve%20Pulse%20Response.pdf
@@IMSAIGuy It is one method to improve bandwidth aside from getting a specialized high bandwidth opto. For example the a application note www.onsemi.com/pub/Collateral/AND8273-D.PDF gives a cascode configuration to improve bandwidth. Search for cascode to find it.
I just wired it up and seems to work great. I wonder why that paper I reference says a simple cascode doesn't work? There might be debate on if Miller is a good term for a phototransistor but it certainly has lots of capacitance what ever you call it, and using the cascode to limit any voltage changes on the collector seems to work fine.
@@IMSAIGuy I discovered this a many years ago when I found out an optocoupler didn't have enough bandwidth for my digital data. I found this trick and it worked very well for me as well. The base is floating so it is non-traditional to think of it as a miller effect I guess, but I have seen the same trick used to improve bandwidth for other photodetector circuits using phototransistors.
Very nice component and can be used to sensitive swr protection. Only need 0.8v to open circuit to protect amplifier of hi swr... very nice video thank you....
Question.....so did you remove the +10v on the opto coupler input and replace it with the input wave at the top of the resistor...? If not...where did you wire to...? This is great stuff..!
So in this case there is possible to use this as a separator for analog signal, yes or no? :) thank you for video once again, all information with one button :)
I have found a really simple one way ICOM civ serial to TTL converter that uses only one transistor. I did try to make this work with a opto isolator instead but it never worked. When I use the transistor side of the opto isolator, it works (not isolated) but as soon try to connect the rs232 side to the diode side, it's doesn't work anymore. Any hint on how I could make this work?
@@IMSAIGuy with the need of an external power supply though right ? The fact I wanted to use that one way was it is working without an external power supply with a single transistor, I thought I could have run an opto coupler that way but it seems more complicated than I expected... Thanks for the tips
I spent 2 hours searching to know how does an optocoupler handles analog signals until I found your video ; answered pretty much all my questions. thanks !
That's exactly what I have been through recently hahaha
Can this linear operation be done with every opto. How to understand it from the data sheet
Excellent video thanks. For anyone who may not know, if you remove the load resistor from the collector lead (pin 4) and positive source and put it between the emitter (pin 3) and ground (or the negative source) and measure between the emitter (pin 3) and ground, the output voltage will go positive as the input side goes positive.
Thank you
Can this linear operation be done with every opto ? How to understand it from the data sheet
@@minshijamusthafa3076 Think of the opto as being a resistor or a switch, which side you put the load on really doesn't matter, configure it to suit your needs. It's just a another series circuit element. Data sheets can't go into every possible configuration.
Excellent demonstration
Great presentation !
The Miller effect is one of the main limiter on the bandwidth. It you use another transistor as a cascode stage then you should be able to improve the frequency response considerably.
I have never seen a cascode on an optocoupler. Do you have direct experience or an example of a product that uses that? you can bootstrap a photo transistor if you have access to the base:
www.epanorama.net/sff/Misc/Optical/Bootstrapping%20Phototransistors%20to%20Improve%20Pulse%20Response.pdf
@@IMSAIGuy It is one method to improve bandwidth aside from getting a specialized high bandwidth opto. For example the a application note www.onsemi.com/pub/Collateral/AND8273-D.PDF gives a cascode configuration to improve bandwidth. Search for cascode to find it.
@@argcargv I'm going to have to try that
I just wired it up and seems to work great. I wonder why that paper I reference says a simple cascode doesn't work? There might be debate on if Miller is a good term for a phototransistor but it certainly has lots of capacitance what ever you call it, and using the cascode to limit any voltage changes on the collector seems to work fine.
@@IMSAIGuy I discovered this a many years ago when I found out an optocoupler didn't have enough bandwidth for my digital data. I found this trick and it worked very well for me as well. The base is floating so it is non-traditional to think of it as a miller effect I guess, but I have seen the same trick used to improve bandwidth for other photodetector circuits using phototransistors.
Amazing video.
Very nice component and can be used to sensitive swr protection. Only need 0.8v to open circuit to protect amplifier of hi swr... very nice video thank you....
Since this has a 80kc response, i would imagine this would work great for audio up to 20kc. Great vid, thanks. 👍
Very useful information. TKS !
Gnd of the opto grom the side of controller, better not to be common with others side GND.
Question.....so did you remove the +10v on the opto coupler input and replace it with the input wave at the top of the resistor...? If not...where did you wire to...? This is great stuff..!
yes
Can this linear operation be done with every opto. How to understand it from the data sheet
So in this case there is possible to use this as a separator for analog signal, yes or no? :) thank you for video once again, all information with one button :)
Yes you can!
Good enough for audio or midi.
I have found a really simple one way ICOM civ serial to TTL converter that uses only one transistor. I did try to make this work with a opto isolator instead but it never worked. When I use the transistor side of the opto isolator, it works (not isolated) but as soon try to connect the rs232 side to the diode side, it's doesn't work anymore. Any hint on how I could make this work?
the led in the optocoupler needs more current than the base of a transistor.
@@IMSAIGuy ish... how can I obtain that with a low output like a RS232 level ? The opto coupler is a 4N25.
@@Aleziss put a transistor in front of the optocoupler. the RS232 will turn on the transistor, the transistor will turn on the LED
@@IMSAIGuy with the need of an external power supply though right ? The fact I wanted to use that one way was it is working without an external power supply with a single transistor, I thought I could have run an opto coupler that way but it seems more complicated than I expected... Thanks for the tips
@@Aleziss You could try a current loop
Great "show n tell", thanks.