Electronics > Projects, Designs, and Technical Stuff
limitation of opamp in the single supply differential mode
ebastler:
--- Quote from: VanitarNordic on April 12, 2019, 05:22:05 pm ---
--- Quote ---So I don't understand the second paragraph of your quoted post.
--- End quote ---
if you don't have a technical point, please stay out of this. I did not ask you to teach ethical points. That was my comment just for Ian.
--- End quote ---
Sorry, but you made a very general, sweeping, moral statement about the bad behavior patterns of engineers "in general". That's what moved the discussion into the realm of "ethics" for me, if you want to use that term.
--- Quote from: VanitarNordic on April 12, 2019, 05:28:50 pm ---I already got the technical answer and solved the problem. Thanks for all technical contributions
--- End quote ---
Fair enough. See you next year! ;)
VanitarNordic:
--- Quote ---Fair enough. See you next year! ;)
--- End quote ---
You don't reply in that case and stay out of this. you have made no contribution here. if you want to continue to your moral things, do it, but I'll not reply anymore.
Zero999:
--- Quote from: VanitarNordic on April 12, 2019, 02:34:52 pm ---
--- Quote ---Anyway, back on topic. The op-amp should be run off the 12V rail. An AC coupled differential amplifier could be used.
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so you confirm my word that when the sensor is VCC referenced (+12V), then the opamp should be at least 12V and a 3.3V opamp cannot do the best job
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I was a bit confused when I made that statement.
If the peak to peak value of the ripple on the 12V supply plus the input signal you're trying to measure is under the op-amp's input voltage range than it should be fine.
In other words, assume the op-amp is run off 3.3V and will work with its inputs down to -0.3V and up to 3.6V (300mV beyond either rail is pretty common for most rail to rail op-amps), then it should work, as long as the ripple on the 12V plus your signal is under3.9V peak to peak. There should also be protection diodes between the op-amp inputs and its positive power supply rail, assuming it doesn't have them built-in.
mikerj:
--- Quote from: VanitarNordic on April 12, 2019, 06:00:30 pm ---
--- Quote ---Fair enough. See you next year! ;)
--- End quote ---
You don't reply in that case and stay out of this. you have made no contribution here. if you want to continue to your moral things, do it, but I'll not reply anymore.
--- End quote ---
You seem like a real piece of work. You are the one that came here asking for help remember?
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