LM317T Adjustable Voltage Regulator (TO-220 Package)

When a standard fixed-voltage regulator (like a 5-Volt 7805 or 3.3-Volt LD33V) doesn’t match the specific power requirements of your project, the LM317 is the universal fallback that every electronics designer keeps in their parts bin. This is an adjustable three-terminal linear voltage regulator capable of supplying over 1.5 Amps of current over an exceptionally wide output range. Instead of being locked to a single voltage at the factory, the LM317 uses a reference pin that allows you to set the output to anywhere from 1.25 Volts all the way up to 37 Volts by simply using a pair of standard external resistors.

Because it is a linear regulator, it provides incredibly clean, low-noise power that is highly preferred for sensitive analog circuits and audio amplifiers. However, it achieves this smooth regulation by shedding the excess voltage as pure heat. Housed in the industry-standard TO-220 package, it features a heavy metal backing tab designed to be bolted to an aluminum heatsink, allowing it to safely dissipate that thermal energy while keeping your power supply rock-solid.

Key Features & Functional Advantages

• Fully Adjustable Output: Gives you complete freedom to set any custom voltage between 1.25 Volts and 37 Volts using just a simple external resistor divider network.

• High Current Capacity: Comfortably provides up to 1.5 Amps of continuous output current (provided adequate heatsinking is used).

• Ultra-Clean Power: Being a linear regulator, it does not produce the high-frequency switching noise that buck converters do, making it ideal for sensitive audio and radio frequency applications.

• Indestructible Safety Features: Features built-in internal thermal overload protection and short-circuit current limiting. If it gets too hot or a wire crosses, it safely shuts itself down instead of catching fire.

• Constant Current Capability: Beyond regulating voltage, the LM317 can be cleverly wired with a single resistor to act as a highly accurate constant-current source, perfect for driving high-power LEDs or charging batteries safely.

Perfect For

• Variable Bench Power Supplies: The foundational component for building your own adjustable electronics lab power supply.

• Custom Battery Chargers: Ideal for creating precise, safe charging circuits for Lead-Acid, NiCd, or NiMH battery packs.

• Analog Audio Circuits: Providing perfectly smooth, noise-free power to sensitive pre-amplifiers and operational amplifier arrays.

• Laser and LED Driving: Easily configured as a current limiter to protect sensitive, high-power laser diodes and customized LED arrays from burning out.

Technical Specifications

• Device Type: Linear Voltage Regulator

• Output Type: Adjustable

• Input Voltage Maximum: Up to 40 Volts DC

• Output Voltage Range: 1.25 Volts to 37 Volts DC

• Maximum Output Current: 1.5 Amps

• Voltage Drop-Out: Typically requires the input voltage to be at least 2 to 2.5 Volts higher than your desired output voltage

• Package Type: 3-Pin TO-220 (Vertical through-hole with metal heatsink tab)