AVR-Chat

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>What method do you recomend for sourcing +V and -V to the opamp?

Analog and digital grounds ideally are separated, and meet under the micro. I use 0 ohm resistors, since it's an easy way to fool your cad package into considering AGND and DGND as separate things.   

I take VCC through a small resistor (1-10 ohms) to AVCC, with a large-ish cap to AGND.
Inductors are more effective, but also more expensive.  I've not yet needed to resort to the inductor solution.