I've designed an active bandpass filter based on the one described in this article http://www.bu.edu/eng/courses/ek307/documents/ActiveFilterNotes.pdf (section 13.3.4). However, I want to use a single ended supply, and I want use a non-inverting configuration. I've designed a circuit (below) and run some spice simulations, and everything is working fine.
But then I noticed that R3 is connected to the negative rail (GND) not my virtual ground (Vcc/2). My instinct tells me that R3 should terminate at Vcc/2 but after some experimentation I found that it doesn't matter where it goes - ground, Vcc, Vcc/2, 10 megavolts - no difference.
How can that be? Can someone explain exactly what's going on here? Am I correct that R3 should terminate at Vcc/2?