LM317 Adjustable Positive Voltage Regulator IC – 1.25V to 37V, 1.5A (TO-220 / DIP)

LM317 Adjustable Positive Voltage Regulator IC – 1.25V to 37V, 1.5A

The LM317 is the world's most popular adjustable positive voltage regulator – a three-terminal IC that delivers any output voltage from 1.25V to 37V at up to 1.5A, set by just two external resistors. With built-in thermal shutdown, overcurrent protection, and safe operating area protection, it's virtually indestructible in normal use. The LM317 has been in continuous production since 1970 and remains the standard choice for adjustable linear power supply design, battery charging, and LED driving.

Electrical Specifications

• Part Number: LM317 / LM317T (TO-220) / LM317L (TO-92)
• Output Voltage Range: 1.25V – 37V (adjustable)
• Output Current: 1.5A (continuous, with heatsink)
• Input Voltage: 3V – 40V DC (must be ≥3V above Vout)
• Reference Voltage: 1.25V (between Output and Adjust pins)
• Output Accuracy: ±1.5% (typical)
• Line Regulation: 0.01%/V | Load Regulation: 0.1%
• Operating Temperature: 0°C to +125°C
• Built-in thermal shutdown, overcurrent, and SOA protection

Output Voltage Formula

Vout = 1.25V × (1 + R2/R1)

With R1 = 240Ω: R2 = 720Ω → 5V | R2 = 2.16kΩ → 12V | R2 = 6.96kΩ → 37V

Typical Applications

• Adjustable bench power supply: Variable voltage source for electronics prototyping
• Battery charger: Constant-voltage charging for NiMH, lead-acid, and Li-ion batteries
• LED driver: Constant-current LED driving with sense resistor
• Motor speed control: Variable voltage for DC motor speed adjustment
• Electronics education: Teaching voltage regulation and resistor divider theory

Package Contents

• 1 × LM317 adjustable positive voltage regulator IC

The world's most popular adjustable voltage regulator – the LM317 delivers any voltage from 1.25V to 37V at 1.5A with just two resistors and built-in protection.