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Part Number: OPA4172
HeyI've created my first PCB design using the design from http://www.ti.com/tool/TIPD181 as a basisfor the quad channel preamp OPA4172.circuit wire up:https://imgur.com/1e0fYMwPcb Design without ground plane showing:https://imgur.com/DmMtIYb
Pcb with ground plane:https://imgur.com/5kgW2RJ
My issue is that all my inputs (mic 1-4) are all showing up across all outputs. Eg; mic 1 will show at all outputs, 2 at all outputs etc etc.I've tried making another circuit with no ground plane in the case that the PCB tracks were crossing with the outputs but it sounds awful and still has the same issue.Thanks
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In reply to Andreas Metaxas:
In reply to kai klaas69:
Hi Andreas, please don't feel offended, but the layout is highly disadvantageous. :-) You should move the components much closer to the OPAmp. This is especially true for the decoupling caps and filtering caps. You should avoid long copper traces and minimize loop areas. And last but not least, you must strictly separate input and output lines. If you use microphones with cabling, take shielded cables and connect the cable shield to signal ground. Again, what microphones are you using? Kai
Fair enough i was hoping that there would be another reason on this weird crossfeeding.I've got 4 individual ones ,although through-hole variant so that should cover me till i order the soic ones in.Thanks for taking the time to answer my query !
Hey Sorry i didnt answer your prior questionIm using a cmi-5247tf-kdont pay attention to that 1uf cap as thats was a mistake
Here are a few blogs I've written on PCB layout of an op amp to help in the next revision of your PCB.
The Basics: How to layout a PCB for an op amp
How to layout a PCB for high-performance, low-side current sensing designs
Kai is correct in that long cabling can effect the stability of the amplifier so I recommend either connecting the microphone to the PCB or changing the feedback capacitor to ensure the amplifier is stable with the cable capacitance included in your design.
In reply to Tim Claycomb:
Sorry, i had just checked my image that i had attached at the start of the post and had noticed i attached the wrong image.For some reason my feedback resistor should be 12p, along with r4 and c6 being 50 olm and 2.2uf respectfully.Either way i appreciate the assistance, i resolved the issue using 4 separate boards until i can produce an ideal boardRegardsAndreas
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