I need help with a basic circuit to allow variable gain (basically, an analog volume control) with a single-supply op-amp. I’ve done dozens of dual-rail audio op-amp circuits, but single supply makes things considerably more difficult with AC signals, and I’ve never really learned how to cope with that.
Here’s what I want to do: There’s a buffer stage, then I need a volume control (unity to neg. infinity), then various filters. Oddly enough, I can find good examples of HP/LP/BP filters from TI app notes, but a simple potentiometer gain stage is nowhere to be found. Anyone have a good example, or at least better Google-Fu than I?
I’ve attached the little I have so far, with the “?” being the gain stage. VCC/2 (the signal ground) is accomplished via a voltage divider feeding an op-amp to provide a stable 2.5v reference (given a 5v rail).