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- Nov 28, 2011
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You probably should have a decoupling capacitor between pins 4 and 11 of the LM324. A 10 µF electrolytic in parallel with a 0.1 µF ceramic is good. This will help the amplifier to be stable.
Your first circuit has the op-amp inputs mislabelled. The pin numbers (2 at the top and 3 at the bottom) are right, but the "+" and "-" markings are reversed.
That circuit may not work very well, especially at low illumination, because the LM324's output is not guaranteed to pull down as far as its negative supply pin. This circuit would normally be operated from split supplies, i.e. a positive rail AND a negative rail.
I don't know why you want to add a second op-amp, and you also have the inputs reversed on the second op-amp, but I found a similar circuit at http://www.eetimes.com/document.asp?doc_id=1225591 which may be useful to you.
Your first circuit has the op-amp inputs mislabelled. The pin numbers (2 at the top and 3 at the bottom) are right, but the "+" and "-" markings are reversed.
That circuit may not work very well, especially at low illumination, because the LM324's output is not guaranteed to pull down as far as its negative supply pin. This circuit would normally be operated from split supplies, i.e. a positive rail AND a negative rail.
I don't know why you want to add a second op-amp, and you also have the inputs reversed on the second op-amp, but I found a similar circuit at http://www.eetimes.com/document.asp?doc_id=1225591 which may be useful to you.
