# LM317

## LM317 Voltage Calculator

- Details
- Category: Voltage regulators
- Published: Monday, 01 September 2008 09:56
- Written by Justblair

This LM317 Calculator can be used to choose the correct resistor values for the LM117-LM317 Voltage regulators.

For an LM317, LM217 or LM117 you can either select your resistor values from the E24 decade list to calculate the LM317 output Voltage, or input your target voltage and value for R1 to get a "ideal" R2 resitor value for the LM317. This Ideal resistor of course may not exist, but sometimes can be made up from more than one resistor, or alternatively will allow you to estimate the optimum variable resistor value to fine tune your LM317 circuit.

**Typical Values for R1 are between 120Ω and 240Ω and you would be well advised to stick to values in this range.**{iframe}lm317.htm{/iframe}

The calculation comes from the Dataseet for the LM117-LM317, although omits the error correction from the calculation. However as resitors have a tolerance of 1-10% in comparison such a small error correction is probably irrelavent for most builders.