The LM317 itself it not connected to ground.The Vout is regulated to 1.25V higher than Vadj.The output voltage is set higher than 1.25V by lifting the Vadj above ground level.The voltage over R1 is always 1.25V. The current through R1 is 1.25/R1.That same current has to go through R2. Also the current of the LM317 itself is going through R2, but that is only 50uA, so that is not in the formula.If R1 = 100 ohm, and R2 = 200 ohm. The voltage over R1 is 1.25V and over R2 is 2.50V. The output will be 1.25+2.50 = 3.75V
Am I missing something?
So it does not use the voltage divider rule in this case?
I found this more detailed diagram: http://www.globalspec.com/reference/81979/203279/chapter-4-linear-power-suppliesAnd got abit more confused =(Can some kind soul explain to me how this circuit works? As in how are the voltages at the inverting and non-inverting input determined and stuffThanks in advance
@don, Vin is not part of the math for calculating Vout.
Quote@don, Vin is not part of the math for calculating Vout.It most certainly is. We aren't talking about perpetual motion here. You can't get any voltage out unless you put some voltage in.I think you missed where I defined Vin, it isn't the same as the Vin that cropped up in the link in reply #2.Don