Let's say I have a supply of 12v, and a 7805 5v voltage regulator. If we use this 7805 between the 12v and GND we get an additional 5v line. Now can we use the 12v and the 5v to power a load that requires 7v (=12v-5v)?
I'm asking because this would mean that 7805 has to deal with current going in the opposite direction than in the more "usual" circuits. If this is possible, does that hold generally for most voltage regulators or is that highly dependent on the particular model?