Lm317 Output Voltage Calculator

LM317 Output Voltage Formula:

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

Output Voltage (V_out):

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1. What is the LM317 Output Voltage Calculator?

The LM317 Output Voltage Calculator helps determine the output voltage of an LM317 voltage regulator based on the values of two external resistors (R1 and R2). The LM317 is an adjustable positive voltage regulator that can supply more than 1.5A of output current.

2. How Does the Calculator Work?

The calculator uses the LM317 output voltage formula:

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

Where:

\( V_{out} \) — Output voltage in volts
\( R1 \) — First resistor value in ohms
\( R2 \) — Second resistor value in ohms
1.25 — Reference voltage of LM317 in volts

Explanation: The formula calculates the output voltage based on the ratio of the two external resistors R2 and R1, with a fixed 1.25V reference voltage.

3. Importance of Voltage Calculation

Details: Accurate voltage calculation is crucial for designing power supply circuits, ensuring proper operation of electronic devices, and preventing damage to components from incorrect voltage levels.

4. Using the Calculator

Tips: Enter resistor values R1 and R2 in ohms. Both values must be positive numbers greater than zero. The calculator will compute the output voltage based on the standard LM317 formula.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical reference voltage for LM317?
A: The LM317 typically has a reference voltage of 1.25V between the output and adjustment terminals.

Q2: What are the recommended values for R1?
A: R1 is typically chosen between 120-240 ohms to ensure proper regulation and minimum load current requirements.

Q3: What is the maximum output voltage of LM317?
A: The LM317 can typically provide output voltages up to about 37V, though this depends on the input voltage and power dissipation limits.

Q4: Are there current limitations for this calculation?
A: The formula assumes the adjustment pin current (typically 50-100μA) is negligible compared to the current through R1 and R2.

Q5: Can this calculator be used for other voltage regulators?
A: This specific formula applies to LM317 and similar adjustable regulators. Other regulators may have different reference voltages or formulas.