1. What is the LM337 Resistor Calculation?

The LM337 is an adjustable negative voltage regulator that requires an external resistor to set the output current. The resistor value determines the current flowing through the circuit.

2. How Does the Calculator Work?

The calculator uses the LM337 resistor equation:

Where:

• \( R \) — Resistor value in ohms (Ω)
• \( I \) — Desired current in amperes (A)
• 1.25 — Reference voltage of LM337 (V)

Explanation: The equation calculates the resistor value needed to achieve a specific current output with the LM337 regulator.

3. Importance of Proper Resistor Selection

Details: Selecting the correct resistor is crucial for proper current regulation, circuit protection, and achieving desired performance from the LM337 regulator.

4. Using the Calculator

Tips: Enter desired current in amperes. The value must be positive and greater than zero. The calculator will output the required resistor value in ohms.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical current range for LM337?
A: The LM337 can typically handle currents from 1.5A down to very low currents, but check the datasheet for specific limits.

Q2: What resistor type should I use?
A: Use precision resistors (1% tolerance or better) for accurate current regulation, especially at lower currents.

Q3: How does temperature affect the calculation?
A: The reference voltage (1.25V) has some temperature dependence. For critical applications, consider temperature coefficients.

Q4: Can I use this for positive regulators like LM317?
A: The same formula works for LM317, as it also has a 1.25V reference between output and adjust pins.

Q5: What power rating should the resistor have?
A: Calculate power using P = I² × R and choose a resistor with at least 2× the calculated power for safety margin.