LM117/LM317A/LM317 - 3-Terminal Adjustable Regulator - Features and Typical Applications

Nov 2, 2026

LM117/LM317A/LM317 is a series of adjustable 3-terminal positive voltage regulators supplying more than 1.5A across a 1.2V to 37V output range. The design is easy to set using only two external resistors, with improved line and load regulation compared with fixed regulators. Integrated protection includes current limit, thermal overload protection, and safe area protection, remaining functional even with an open adjustment terminal. Input bypassing and optional output capacitance support transient performance, ripple rejection, and flexible applications such as adjustable switching, programmable regulation, and precision current regulation.

LanguageEnglish

CategoryTechnology

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Pages30

Reading Time1 h 16 min

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General Description

Features

Typical Applications

LM117/LM317A/LM317 Package Options

Connection Diagrams

Ordering Information

LM117,LM317 LM117/LM317A/LM317 3-Terminal Adjustable Regulator Literature Number: SNVS774L LM117/LM317A/LM317 3-Term ina l Adjustab le Regulator © 2011 National Semiconductor Corporation 9063 [www.national.com](www.national.com) | | February 25, 2011
LM117/LM317A/LM317 | | | --- | --- | --- | | 3-Terminal Adjustable Regulator | | | | General Description
The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and handled.
In addition to higher performance than fixed regulators, the LM117 series offers full overload protection available only in IC's. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected.
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.
Besides replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as | | the maximum input to output differential is not exceeded, i.e. , avoid short-circuiting the output.
Also, it makes an especially simple adjustable switching regulator, a programmable output regulator, or by connecting a fixed resistor between the adjustment pin and output, the LM117 can be used as a precision current regulator. Supplies with electronic shutdown can be achieved by clamping the adjustment terminal to ground which programs the output to 1.2V where most loads draw little current.
For applications requiring greater output current, see LM150 series (3A) and LM138 series (5A) data sheets. For the negative complement, see LM137 series data sheet.
Features
■ Guaranteed 1% output voltage tolerance (LM317A)
■ Guaranteed max. 0.01%/V line regulation (LM317A)
■ Guaranteed max. 0.3% load regulation (LM117)
■ Guaranteed 1.5A output current
■ Adjustable output down to 1.2V
■ Current limit constant with temperature
■ P+ Product Enhancement tested
■ 80 dB ripple rejection
■ Output is short-circuit protected | | Typical Applications
1.2V–25V Adjustable Regulator

906301
Full output current not available at high input-output voltages
*Needed if device is more than 6 inches from filter capacitors.
†Optional—improves transient response. Output capacitors in the range of 1μF to 1000μF of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients.
| | LM117/LM317A/LM317 Package Options
Part
Number Suffix Package Output
Current LM117, LM317 K TO-3 1.5A LM317A, LM317 T TO-220 1.5A LM317 S TO-263 1.5A LM317A, LM317 EMP SOT-223 1.0A LM117, LM317A, LM317 H TO-39 0.5A LM117 E LCC 0.5A LM317A, LM317 MDT TO-252 0.5A
SOT-223 vs. TO-252 (D-Pak) Packages

906354
Scale 1:1 | LM117/LM317A/LM317 [www.national.com](www.national.com) 2 | Connection Diagrams
TO-3 (K) Metal Can Package

906330
CASE IS OUTPUT
Bottom View
Steel Package NS Package Number K02A or K02C
TO-263 (S) Surface-Mount Package

906335
Top View
TO-263 (S) Surface-Mount Package

Side View906336 NS Package Number TS3B | TO-39 (H) Metal Can Package

9063

FAQs

What output voltage range and maximum output current do LM117/LM317A/LM317 support?

The regulator series supports a 1.2V to 37V output range and can supply in excess of 1.5A output current.

How is the output voltage set for this adjustable regulator?

Only two external resistors are required to set the output voltage.

What protection features are built into the LM117/LM317A/LM317?

The IC includes current limit, thermal overload protection, and safe area protection, and overload protection remains functional even if the adjustment terminal is disconnected.

Nov 2, 2026

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