One of the conditions for oscillation is that the (regenerative) feedback loop must provide a 180 degree phase shift. This is due to the fact that, for a regenerative effect, the signal must undergo n*360 degrees phase shift: 180 from the amplifier and another 180 from the feedback network. My question is, doesn't this depend on the type of configuration used with the amplifier? For instance, a common-source amplifier is an inverting configuration, so this condition would certainly apply. For a common-drain, or source follower, configuration though, the output is in phase with the input, isn't it? That also brings up another doubt I have. I have never been able to "pin point" exactly what it is in an inverting configuration that makes...inverting. Some brief explanation would be greatly appreciated.