EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Shale on February 01, 2012, 03:18:34 pm
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I was looking at Daves power supply design. I have looked at both rev A and rev B and there is something I can not figure out why it was done. If you look at rev B on the ADC, the op amps have different voltage sources. One has the voltage source, while the other also has a cap and a ground. It i the same with the op amps in the PUS area of the schematic as well. Why is this?
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Those are decoupling (aka bypass) caps. They appear on only one of the two opamp symbols because each pair of opamps is actually contained within the same IC and that IC has only one power pin to be bypassed. Notice how the opamps near the ADC are labeled U12A and U12B rather than U12 and U13. This is to designate that they are two parts of the same package.
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Also, if you're trying to understand the circuit then be aware. There was an error in one of the revisions, cant remember which, it was in the video.
One of the opamps had its inputs reversed.
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it was revB, he cut the wrong trace while pretty-ing it up for us :)
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Those are decoupling (aka bypass) caps. They appear on only one of the two opamp symbols because each pair of opamps is actually contained within the same IC and that IC has only one power pin to be bypassed. Notice how the opamps near the ADC are labeled U12A and U12B rather than U12 and U13. This is to designate that they are two parts of the same package.
Ok. that makes better sense. Thank you for clarifying that for me.
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Those are decoupling (aka bypass) caps. They appear on only one of the two opamp symbols because each pair of opamps is actually contained within the same IC and that IC has only one power pin to be bypassed.
Wait, did dave forget bypass caps in his original design?
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Those are decoupling (aka bypass) caps. They appear on only one of the two opamp symbols because each pair of opamps is actually contained within the same IC and that IC has only one power pin to be bypassed.
Wait, did dave forget bypass caps in his original design?
Bypass capacitors are not required on every op-amp package, but it is just a good idea. With bypass capacitors, you tend to want to have too many rather then too few.