math question

[Clark101]

i am having trouble with this equation :

Vout = 1.25V (1+ R2/R1) + IAdjR2

i am trying to solve for R2 (it is for getting my voltage right with my portable using one of those LM317T) any help would be awesome..

[kibble]

You need to plug in the "voltage out" into the equation and at least one known resistor value to make the equation really easy.

[Clark101]

Vout = 7.5 volts and R1 = 240 and IAdj = 100 uA

the problem is getting that +1 out of the formula..

[kibble]

Distribute the 1.25 into 1+R2/R1. If I did it right, the value for R2 would be 1.18K, or 1.2K would probably be the closest value to that. I would try it out and check the voltage before powering your circuit.

[vskid]

For those to lazy to do the math, here is a calculator for it. http://www.electronics-lab.com/articles/LM317/" onclick="window.open(this.href);return false;