audioguru: I have not read your posted tutorial and therefore I do not know whether I agree with it or not. I do not intend to continue to go head to head with you or anyone else regarding simple op-amp theory. In my original post, I pointed out that you do not need a bias voltage from the power supply added to an op-amp that is run from a bipolar supply. The inputs are referenced to ground, which is the center point of a bipolar supply. Perhaps you disagree with this. So be it. Move on. In the circuit that you have posted, I know nothing about it, do not have a parts list, nor do I know what the second IC is, but it appears to be an AC or pulsed active circuit. In which case, the pin with the capacitor connected to it is not floating when the field is collapsing and there is capacitive reactance. Perhaps this is what this circuit is meant to do since there is a DC blocking capacitor at the output of the op-amp. Again, I do not intend to spend time in debate with you. If your purpose here is trying to determine if this circuit works, I must point out that you have spent days in debate when you could breadboard this circuit in minutes to make such a determination. In reference to your comment, "Why ignore me? You might learn something important". I do not think anyone with your attitude would be able to teach me anything. I now fully understand the prior comments posted by ante.