LM317 Voltage and Resistor Calculator

LM317 Voltage and Resistor

The values of the external resistors attached to the LM317, an integrated circuit voltage regulator, determine how much voltage is output.
Through precise configuration of resistor combinations with the LM317, users can establish output voltages appropriate for a range of applications.

Stabilizing and controlling voltage levels in electronic circuits is the main goal of the LM317 voltage regulator with resistors, which guarantees the dependable and constant operation of electrical components.
It is a necessary part of power supply circuits and voltage regulation systems because it offers a way to achieve a stable output voltage in spite of variations in input voltage or changes in load conditions.

Understanding LM317 Voltage and Resistor:

The LM317 serves as a versatile voltage regulator, capable of producing a variety of output voltages (ranging from 1.5V to 37V) by adjusting the resistors R1 and R2. To establish the output voltage, a voltage divider is employed, comprising two external resistors connected sequentially. While the suggested value for R1 stands at 240Ω, alternatives within the range of 100Ω to 1000Ω are also viable.

The LM317 offers versatile applications in circuit design, including configurations like a 0 V to 30 V regulator, adjustable regulators with enhanced ripple rejection, precision current limiters, tracking pre-regulators, and more. When selecting resistors for the LM317, it’s crucial to consider factors like output and input voltages, as well as circuit current requirements to maintain stable output within the desired range.

Here are some key considerations for resistor selection:

– For fixed output voltage, maintain a constant R2/R1 ratio.

– For variable output voltage, ensure a linear variation of R2/R1 with the desired output.

– While the recommended R1 value is 240Ω, alternatives between 100Ω to 1000Ω are feasible.

– Choose R2 value to align with the desired output voltage range.

Additionally, account for resistor power dissipation to manage heat generation, ensuring that it remains within usable limits. The LM317 facilitates the calculation of resistor heat output, indicating suitability if heat dissipation does not exceed 0.4W.

In essence, the LM317, functioning as an adjustable voltage regulator, relies on resistors R1 and R2 to set the output voltage through a voltage divider. Thoughtful resistor selection is pivotal to maintaining stable and desired output voltage levels.


  • Power Supplies
  • Battery Charging
  • Voltage Reference
  • LED Drivers
  • Audio Amplifiers

Finding the LM317 V and R values is made easier using our electrical engineering calculator. This calculator makes it simple to determine the matching R2 value by entering the V and R1 values. This calculator, which was created especially for use in electrical engineering applications, simplifies calculations and assists in determining the ideal resistor values. With the help of our intuitive electrical engineering calculator, you can improve your circuit design and analysis by doing fast and precise calculations for the voltage and resistance values of LM317.

Note : Don’t end with comma ( , )

Resistor 1 (R1)
Resistor 2 (R2)
Voltage Vout


\[V_{out} = 1.25 * \left(1+\frac{R2}{R1}\right)\]


Vout = Output Voltage

R1 = Resistor 1

R2 = Resistor 2

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