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LM311 supply

throbscottle

Well-Known Member
Does anyone know the lowest supply voltage on which the LM311 will actually work? Datasheet says 3.5v but I get the impression it can go lower. I'm hoping for 3v.
I'd go for the MIC6270 or TLV170x but it's expensive to get a hobbyist sized quantity. Any other alternatives?
TIA
 

ChrisP58

Well-Known Member
Most Helpful Member
Does anyone know the lowest supply voltage on which the LM311 will actually work? Datasheet says 3.5v but I get the impression it can go lower. I'm hoping for 3v.
I'd go for the MIC6270 or TLV170x but it's expensive to get a hobbyist sized quantity. Any other alternatives?
TIA
A manufacturers datasheet tells you what you can expect all of their devices to do under what conditions. Many parts may work fine outside of those conditions, but some may not. They may meet some specs, but not all. And while you can get away with more variations in hobby builds, running components outside of the spec limits on production builds is a recipe for disaster.
 

throbscottle

Well-Known Member
That's useful. I know it was a dumb question, but the datasheet puts 3.5 minimum under "recommended operating conditions" rather than as a real minimum - it doesn't give a definitive absolute minimum anywhere. Add to that, I see forum posts elsewhere where they are being used on 3.3v. So I had to ask.
Tumbleweed - when I can get everything else to run on 0v, I'll try it and let you know how it goes, 'k?
 

crutschow

Well-Known Member
Most Helpful Member
Can you use an LM339?
Their operating range goes down to 2V.
 

tumbleweed

Active Member
You'd be better off looking for a comparator spec'd to work at 3.3V.
Even if the lm311 "works" at that low VCC, you'd probably end up with a common mode input range of about 2V.
 

throbscottle

Well-Known Member
Hmmm. I'm trying to tick boxes on a very short "nice to have" list. Refer to this thread so you see where I'm coming from: https://www.electro-tech-online.com/threads/hp-magic.161877/
I got it working with slightly more pedestrian diodes - BAS70. It's still an LM339 in there. However, this is a true "can't have your cake and eat it" circuit. Getting good pulse detection is at the expense of clock signal frequency range, and improving clock detection comes at the expense of fast pulse detection. Those fast clock speeds I mentioned in the other thread are completely out the window. (All of this in simulation - I'm moving house soon and everything is packed away!) The only way out is to use a faster comparator as far as I can see, and the LM311 does very nicely.
I suppose I could just give it a battery option for probing circuits with a low supply voltage - though I don't like the idea. There's just not many affordable alternatives with a wide supply voltage range. I'm not likely to stick it on more than 12v, but the overhead is nice.
 

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