jelliott
Member
If anyone is still paying attention to this thread... I built the circuit shown in Post #4 above by Ericgibbs, and it's not working. It looks like it's probably a problem with the chip, but I'm hoping some of the knowledgeable people on this forum may be able to help me confirm that. I've got 12 V, 2.5 V, and ground in all the right places, but with a 5 V input I'm getting an output > 7 V instead of 0 V. When I adjust the potentiometer that I'm using in position R2 the erroneous output is unchanged, which is what leads me to believe that the chip must be at fault. Any thoughts? (For what it's worth, the chip I'm using is an NTE7144, which is the cross-reference Mouser gave me when I searched for CA3140; as far as I can tell this is a totally legit cross-reference, but since most of my electrical engineering knowledge is strictly theoretical, I'm curious if I've inadvertently made some kind of op-amp cross-referencing faux pas.)
Thanks,
Joe Elliott
Thanks,
Joe Elliott