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LM317 Calculator
Calculate resistor values for LM317 voltage regulator circuits
About LM317 Voltage Regulator
The LM317 is an adjustable positive voltage regulator that can provide a regulated output voltage from 1.25V to 37V. It requires only two external resistors to set the output voltage.
LM317 Design Tips
- Reference Voltage: LM317 has 1.25V reference voltage between ADJ and OUT
- R1 Selection: Use 240Ω for good stability and low quiescent current
- R2 Calculation: R2 = R1 × ((Vout / 1.25) - 1)
- Heat Dissipation: Calculate power dissipation: P = (Vin - Vout) × Iload
- Capacitors: Use 0.1μF ceramic and 1μF electrolytic for stability
- Thermal Management: Use heatsink if power dissipation > 1W