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Comments on Constant Current Load Circuit with Op Amp

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Constant Current Load Circuit with Op Amp

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Hi, I built a constant current load following the circuit from https://www.instructables.com/id/DIY-Constant-current-load/

But my op amp gets destroyed after a few minutes. The transistor or the op amp didnt get hot to the touch. After replacing the op amp the circuit works again for a short time.

Am I at fault or is the circuit wrong? Tested at 10V 0.5A.

Image alt text

P.S. It is working again as of now. But still I have destroyed a couple op amp. Is there a better circuit design? Like mentioned here https://electronics.stackexchange.com/questions/371864/constant-current-load-op-amp-ref-voltage-limit

opamp
posted about 4 years ago
4y ago
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timelyfiasco‭
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General comments (3 comments)
General comments
Andy aka‭ wrote about 4 years ago
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Your circuit is incorrect on the output. The load needs to connect between the source and a positive supply voltage not ground. Your hyperlink doesn't work and you haven't shown the value of the MOSFET source resistor. You haven't mentioned what op-amp supply decoupling you have used either. Assuming you have got the load connected properly, how you have interconnected the parts could have a profound effect on chip reliability.

timelyfiasco‭ wrote about 4 years ago · edited about 4 years ago
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I changed the link. This is for a constant current load tester, for batteries and testing the current rating of buck converters. It works with the load negative connected to ground. MOSFET source resistor is 1ohm. No op-amp supply decoupling.

Andy aka‭ wrote about 4 years ago
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Your circuit WILL NOT work with the load negative connected to ground.