This tool helps you easily calculate the output voltage of an LM317 voltage regulator based on the resistor values you input.
LM317 Calculator
This calculator helps you determine the output voltage for an LM317-based voltage regulator circuit. Enter the values for R1, R2, and Iadj and click “Calculate” to see the result.
How to Use It
- Enter your resistor values (R1 and R2) in Ohms. Typical starting values are R1 = 240Ω.
- Enter the adjustable current (Iadj). It is typically 50μA (0.00005 Amps).
- Click the Calculate button to see the output voltage.
How It Calculates
The calculation uses the LM317 voltage regulator formula:
Vout = 1.25 * (1 + (R2 / R1)) + (Iadj * R2)
The output voltage (Vout) is determined based on the resistances R1 and R2 and the adjustable current Iadj.
Limitations
- The value of Iadj is typically very small (50µA), so its effect on the overall voltage is minimal but necessary for precision.
- This calculator assumes ideal conditions without taking into account tolerances of the resistors.
- Extreme values for R1, R2 or Iadj may result in inaccurate readings.
Use Cases for This Calculator
Calculating Resistor Value for LM317 Voltage Regulator
Enter the desired output voltage and output current of your LM317 circuit to calculate the exact resistor value needed for the voltage regulator setup. By inputting the values, you can ensure a stable and precise output voltage suitable for your project.
Calculating Output Voltage of LM317 Voltage Regulator
If you have your LM317 voltage regulator circuit set up and need to find out the output voltage, simply input the resistor values used in your setup into the calculator. This will help you confirm the expected voltage output of your circuit accurately.
Calculating Power Dissipation in LM317 Voltage Regulator
To determine the power dissipation in your LM317 voltage regulator, input the input and output voltage values along with the output current. This calculation helps you ensure that the LM317 is operating within its specified power limits to prevent overheating.
Calculating Output Current of LM317 Voltage Regulator
If you know the resistor values used in your LM317 voltage regulator setup and want to find out the output current, input those values into the calculator. This will give you the current flowing through your circuit accurately.
Calculating Input Voltage Range for LM317 Voltage Regulator
Input the desired output voltage and output current of your LM317 voltage regulator setup to calculate the acceptable input voltage range. Knowing this range helps you select an appropriate power source that meets the input requirements of the LM317.
Calculating Resistor Ratio for LM317 Voltage Regulator
To determine the resistor ratio needed for your LM317 voltage regulator, input the resistor values used in your circuit setup. This calculation helps you achieve the desired voltage output by adjusting the resistors to the correct ratio.
Calculating Load Regulation of LM317 Voltage Regulator
Input the minimum and maximum load current variations along with the output voltage to calculate the load regulation of your LM317 voltage regulator. This calculation helps you understand how well your circuit maintains a stable output voltage under varying load conditions.
Calculating Efficiency of LM317 Voltage Regulator
If you want to measure the efficiency of your LM317 voltage regulator setup, input the input and output voltage values along with the output current. This calculation helps you evaluate how effectively the LM317 converts input power to the desired output power.
Calculating Ripple Rejection of LM317 Voltage Regulator
Input the input ripple voltage and output voltage to calculate the ripple rejection ratio of your LM317 voltage regulator. This calculation helps you assess how well the LM317 suppresses any input ripple voltage to provide a clean and stable output voltage.
Calculating Thermal Resistance of LM317 Voltage Regulator
To determine the thermal resistance of your LM317 voltage regulator setup, input the power dissipation and temperature difference values. This calculation helps you understand how efficiently the LM317 dissipates heat to prevent overheating and ensure optimal performance.