Electronics > Beginners
Correctly stabilize an opamp current source
soldar:
--- Quote from: ZeroResistance on April 24, 2019, 11:08:56 am --- Will recheck and do the needful.
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"Do the needful." I thought that was an odd turn of phrase and looked it up. It seems it was a formal expression used over a century ago and which has only survived in India. Interesting. One guy says he uses it to mean "I am going to poop". :)
--- Quote --- Grammarly: Do the needful means do that which is needed. It's mainly used in formal written communication, especially when dealing with bureaucracy. It can be preceded by the words “kindly” or “please.” Ideally, it should follow an explanation of a problem that needs to be fixed or a request that is being made.
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ZeroResistance:
--- Quote from: soldar on April 24, 2019, 11:33:29 am ---
--- Quote from: ZeroResistance on April 24, 2019, 11:08:56 am --- Will recheck and do the needful.
--- End quote ---
"Do the needful." I thought that was an odd turn of phrase and looked it up. It seems it was a formal expression used over a century ago and which has only survived in India. Interesting. One guy says he uses it to mean "I am going to poop". :)
--- Quote --- Grammarly: Do the needful means do that which is needed. It's mainly used in formal written communication, especially when dealing with bureaucracy. It can be preceded by the words “kindly” or “please.” Ideally, it should follow an explanation of a problem that needs to be fixed or a request that is being made.
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:-DD Lol good catch and thanks for the explanation!
ZeroResistance:
--- Quote from: imo on April 24, 2019, 11:32:44 am ---I've done a stability analysis and it seems the circuit is stable per se (44deg phase margin).
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Great going! how on earth did you do that?
In the meanwhile I have got some success with the BJT version (2N3904 + BD139). I tested it upto 2A and it seems OK.
I need a higher current so I'm gonna try a Sziklai pair version next.
Both images attached.
ZeroResistance:
--- Quote from: ZeroResistance on April 24, 2019, 11:46:22 am ---
In the meanwhile I have got some success with the BJT version (2N3904 + BD139). I tested it upto 2A and it seems OK.
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I had checked it on a meter and it showed ok I will get back with scope results next
ZeroResistance:
--- Quote from: ZeroResistance link=topic=182637.msg2365155#msg2365155
I need a higher current so I'm gonna try a Sziklai pair version next.
Both images attached.
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However in hindsight I don't think it might work without certain modifications, considering that a Sziklai output is a PNP and and we would be putting the collector into the feedback loop. There is a phase shift involved here so it might oscillate.
CorrecT?
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