The negative-rail complement of the LM317: a 3-terminal adjustable linear regulator that produces a negative output from -1.2 V down to -37 V at up to 1.5 A, in a TO-220. Two resistors between ADJ and OUTPUT set the voltage (VOUT = -1.25 V times (1 + R2/R1)), and it holds a fixed 1.25 V reference between ADJ and OUT. It brings the same internal current limiting, thermal shutdown, and safe-operating-area protection as the LM317. Note the pinout differs from the LM317: here pin 1 = ADJ, pin 2 = VIN, pin 3 = VOUT. Use it with an LM317 to build a dual-rail supply.

Pinout

Pin	Name	Type	Function
1	ADJUSTMENT	input	Adjustment pin for the output voltage. Connect two external resistors between OUTPUT, ADJUSTMENT, and ground to set the output voltage; typical ADJUSTMENT current is 65 uA (100 uA max). Reference voltage from OUTPUT to ADJUSTMENT is -1.25 V (typ).
2	INPUT	power_in	Negative input supply voltage (V_I). Input-to-output differential voltage range is -2.5 V to -37 V (abs max -40 V). Recommend a 0.1-uF bypass capacitor across the input.
3	OUTPUT	power_out	Regulated negative output voltage (V_O), adjustable from -1.2 V to -37 V. Peak output current 1.5 A (2.2 A typ). Recommend a 1-uF output capacitor for stability.

Key specifications

Parameter	Value
Type	Adjustable negative linear regulator
Output voltage	-1.2 to -37 V
Output current	up to 1.5 A
Reference	1.25 V (ADJ to OUT)
Protection	Current limit + SOA + thermal shutdown
Pinout	1=ADJ, 2=VIN, 3=VOUT
Line regulation	typ. 0.01 %/V
Package	TO-220 (3-lead)

Ordering variants

Same part, different packaging or reel option.

LM337KCT (TO-220)
LM337KTTR (TO-220, tape & reel)

CAD (KiCad official)

Symbol: Regulator_Linear:LM337_TO220
Footprint: Package_TO_SOT_THT:TO-220-3_Vertical
3D model: TO-220 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (25 pp, sha256 9314cd867e85589c, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF