How to set the LM317 voltage

To set the output voltage of the LM317 adjustable voltage
regulator, you use two resistors in a voltage divider configuration between the
output and adjust pin.

LM317 Output Voltage Formula

To set the output voltage of the LM317, you use the following
formula:

Vout = 1.25V × (1 + R2 / R1) + Iadj × R2

Where:

– Vout = Output Voltage

– R1 and R2 = External resistors

– Iadj = Adjustment pin current (typically very small and often
neglected)

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Common Resistor Values

 R1 (Ω)  R2 (Ω)  Approx.
VOUT (V)

———————————————–

 240         0          
 1.25                

 240         720        
 5                   

 240         1440       
 10                  

 240         1920       
 11.25               

Tip: Always add a 0.1 µF capacitor from the adjust pin to ground
for improved ripple rejection.

Important Notes

– Use precision resistors (1% or better) for accurate output.

– Use heat sinks if output current exceeds 500mA.

– Add input and output capacitors (typically 0.1 µF on input, 1 µF
on output) for stability.

For video tutorial:

About The Author

Aniruddh Kumar Sharma

I am an electronics enthusiast.

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