LM317 Adjustment Calculator

Show/Hide:DefinitionsFormulae Instructions

Introduction:

This page allows you to calculate the size/value or resistor required to run an LM317 at the correct voltage.
Click on any of the links at the top of the page to reveal (or hide) more information about this calculator.

Caveats:

If you are reading this paragraph, then you probably don't have JavaScript installed/enabled.
At this point in time the calculators on this site are entirely dependent on JavaScript. Given enough time and money it is hoped to develop a version in the future which will be able to operate independently. Since JavaScript runs on your own computer, rather than on this server, it has been possible to set up this site much more quickly than if a server-side language was used, and it is possible to serve far more pages with the available bandwidth.
If you think that you can assist with this project in any way, then please visit the Support section and leave a message.

Definitions:

V
Output Voltage of the circuit.
R1
Value of Resistor between Vout and Vadj pins, typically specified as 220Ω
R2
Value of Resistor between Vadj and circuit ground.

Formulae:

V = 1.25 * (1 + R2 / R1)

Instructions

  1. Enter a value into each text-box in the form below.
  2. Choose appropriate unit-sizes for each value from each drop-down list.
  3. Hit the ENTER or RETURN key on your keyboard, or press the 'CalcResult' button below the input fields.
  4. A results area will appear at the bottom of the page, showing the required resistance value.
  5. Press the 'Clear Results' button if you wish to discard the current results list, otherwise further calculations will be added to the bottom of the current results list.

See Also:

Enter Data Here
Basic LM317 circuit diagram
LM317 circuit diagram

Results:


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