Real View
LM337Adjustable negative regulator
Build a negative rail—and keep the polarity clear.
LM337 is an adjustable negative linear regulator in the 1.5 A class. It maintains approximately −1.25 V from OUTPUT to ADJ; two resistors establish the output relative to the common return. Its nominal adjustment span is −1.25 to −37 V with sufficient headroom, load and cooling. The front-view TO-220 pins are ADJ, IN and OUT. The metal tab is connected to the negative input. In SOT-223, the broad input tab is also numbered 4, so all four physical contacts are mapped here. This reference follows TI LM337-N, with LM337T/NOPB and LM337IMP/NOPB package views. A −9 V-to−5 V example shows the divider, required output capacitor and reversed capacitor polarity. The SMD order has an extended temperature range, but the common electrical table below retains the datasheet’s stated 0–125°C LM337-N conditions.
3Physical pins
LM337T/NOPBTO-220
Manufacturer-referencedTexas Instruments
Pin diagram
Select a pin to explore its connection
Highlight
LM337TO-220Front view · marking toward you · ADJ1, IN2, OUT3
LM337SOT-223Top view · ADJ1, IN2, OUT3 left · input tab 4 right
Click a lead or use the arrow keys. Front view · marking toward you · ADJ1, IN2, OUT3
PIN 1 · Adjustment and feedback
Floating adjustment terminalADJ
Function
The regulator holds OUTPUT approximately 1.25 V below ADJ.
How to connect
Connect R1 from OUT to ADJ and R2 from ADJ to the common return.
Electrical note
ADJ is not ground. Adjustment current flows into this terminal.
PIN 2 · Supply
Negative input and metal tabIN
Function
Accepts a negative supply more negative than the required output. The TO-220 tab and SOT-223 tab 4 are also IN.
How to connect
Connect −9 V in the example; keep the live input tab isolated from grounded metal.
Electrical note
This pin assignment differs from positive LM317/LM350 regulators.
PIN 3 · Negative output
Regulated negative outputOUT
Function
Supplies the load at a controlled negative voltage relative to the common return.
How to connect
Connect R1, the load and the required output capacitor here.
Electrical note
Polarized output capacitors have their positive end at the common return, not at OUT.
PIN 4 · Supply
SOT-223 input tabIN / TAB
Function
The broad SOT-223 contact is internally connected to input lead 2.
How to connect
Connect to the negative input copper and provide an adequate thermal path.
Electrical note
This is a separate physical contact on the same IN node; it is not ground.
Key specifications
OUT sits about 1.25 V below ADJ. The divider lifts ADJ below the common return, setting a negative output. Keep the package pinout and capacitor polarity explicit.
Nominal reference−1.25 V · OUT minus ADJ
Adjustment span−1.25 to −37 V · requires headroom
Current class1.5 A · thermal and safe-area limits
Common electrical range0–125 °C junction · see package notes
Package details
LM337T/NOPB · TO-220
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | LM337T/NOPB |
| Package | TO-220 |
| Connections | 3 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | NDE |
| Thermal reference | 0–125°C operating junction; tab = IN |
Operating reference
TI LM337-N electrical column
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Nominal output adjustment | −1.25 to −37 V | With adequate differential voltage, loading and cooling |
| TO-220 order range | 0–125°C junction | LM337T/NOPB |
| SOT-223 order range | −40–125°C junction | LM337IMP/NOPB; do not extend the 0–125°C electrical table implicitly |
| Reference at 25°C | −1.213 / −1.25 / −1.287 V | Manufacturer MIN / TYP / MAX signed entries |
| Reference over stated LM337-N range | −1.20 / −1.25 / −1.30 V | 0–125°C; stated differential and load conditions |
| Adjustment-pin current | 65 µA typical; 100 µA maximum | Flows into ADJ |
| Adjustment current change | 2 µA typical; 5 µA maximum | 10 mA–IMAX; 3–40 V differential; 25°C |
No specifications match. Try a parameter name or a unit.
Electrical test baseline: 5 V input-output differential and 0.5 A load for TO-220/SOT-223, unless specified. Observe the source power conditions.
Regulation and noise
Constant-junction pulse measurements
Manufacturer specifications 8 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Line regulation at 25°C | 0.01%/V typical; 0.04%/V maximum | 3–40 V differential; 10 mA load |
| Line regulation over stated range | 0.02%/V typical; 0.07%/V maximum | 3–40 V differential |
| Load regulation at 25°C | 0.3% typical; 1% maximum | 10 mA–IMAX |
| Load regulation over stated range | 0.3% typical; 1.5% maximum | Constant-junction test conditions |
| Thermal regulation | 0.003%/W typical; 0.04%/W maximum | 10 ms pulse; 25°C |
| Ripple rejection without CADJ | 60 dB typical | −10 V output; 120 Hz |
| Ripple rejection with 10 µF CADJ | 66 dB minimum; 77 dB typical | −10 V output; 120 Hz |
| Output noise | 0.003% of output typical | RMS; 10 Hz–10 kHz; 25°C |
No specifications match. Try a parameter name or a unit.
Typical values are not guaranteed extremes.
Minimum load and current limiting
Current capability depends on voltage drop
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Minimum load at ≤40 V differential | 2.5 mA typical; 10 mA maximum | Guarantee minimum current to maintain regulation |
| Minimum load at ≤10 V differential | 1.5 mA typical; 6 mA maximum | Manufacturer test condition |
| Current limit at ≤15 V differential | 1.5 / 2.2 / 3.7 A | Minimum / typical / maximum; DCY and NDE within power limits |
| Current limit at 40 V differential | 0.15 A minimum; 0.4 A typical | 25°C; safe-area limit reduces available current |
| Example divider | 1.25 / 110 ≈11.36 mA | Contributes to total output current |
| Divider lower bound | 1.20 / 111.1 ≈10.80 mA | 110 Ω at +1% and 1.20 V reference magnitude |
No specifications match. Try a parameter name or a unit.
A 1.5 A class regulator cannot supply full current at every differential voltage or without cooling.
Capacitors and polarity
Negative rails reverse the polarized capacitor orientation
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Required output capacitor | 1 µF solid tantalum or 10 µF aluminum electrolytic | Required for stability; close to OUT and return |
| Input bypass | 1 µF solid tantalum | Required if more than 4 inches from the supply filter; used locally here |
| Positive capacitor terminals | Common return / GND | Negative ends connect to negative IN or OUT |
| Optional adjustment bypass | Improves ripple rejection | Evaluate discharge protection when added |
| Output discharge diode | Review when CL exceeds 20 µF | Source protection circuit diverts discharge during input short |
| Adjustment discharge diode | Review with CADJ >10 µF and output magnitude >25 V | Follow the source protection circuit |
| Example output capacitor | 1 µF solid tantalum, suitably voltage-rated | An arbitrary ceramic substitute is not assumed |
No specifications match. Try a parameter name or a unit.
The common return is the more positive node in this circuit.
Heat and the input tab
Manufacturer thermal metrics · mounting matters
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 θJA reference | 22.9°C/W | SNVS778F test-board metric; not a universal bare-package value |
| SOT-223 θJA reference | 58.3°C/W | Board copper and mounting strongly affect actual results |
| TO-220 θJC(bottom) | 1°C/W | Manufacturer package metric |
| Live tab | IN in both packages | SOT-223 contact 4 is connected to pin 2 |
| Nominal pass loss | (9 − 5) × (0.100 + 0.01136) ≈0.445 W | At 100 mA load plus divider |
| Absolute differential limit | 40 V | Stress limit; use operating headroom and power constraints |
| Internal protection | Current, thermal and safe-area limiting | Not a substitute for normal thermal design |
No specifications match. Try a parameter name or a unit.
Use the correct case/interface/heatsink or board model when estimating junction temperature.
A nominal −5 V supply
−9 V input · 110 Ω / 330 Ω divider
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| R1 from OUT3 to ADJ1 | 110 Ω, 1% | Divider current about 11.36 mA |
| R2 from ADJ1 to GND | 330 Ω, 1% | R2/R1 = 3 |
| Ideal output | −1.25 × (1 + 330/110) = −5.00 V | Before adjustment current and tolerance |
| Typical IADJ correction | −65 µA × 330 Ω = −21.45 mV | Nominal result approximately −5.021 V |
| Load | 50 Ω, at least 1 W | Between GND and OUT; about 100 mA / 0.5 W |
| Input headroom | Approximately 4 V magnitude | −9 V input, −5 V output |
| Common return | Supply return, R2, load and capacitor positive ends | No dedicated ground pin on the IC |
No specifications match. Try a parameter name or a unit.
Nominal calculations; verify the actual loaded voltage and temperatures.
Physical package reference
LM337T/NOPB · TO-220
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 front-view lead order | 1 ADJ; 2 IN; 3 OUT | Marking toward you; leads down |
| SOT-223 top-view contacts | 1 ADJ; 2 IN; 3 OUT; 4 IN tab | Three narrow leads opposite a broad input tab |
| Selected pitch | 2.54 mm | See physical pin map and footprint |
| Selected operating range | 0–125°C operating junction; tab = IN | Package-specific note |
| Output versus tab | OUT is pin 3; tab is IN | Do not use a positive-regulator tab assumption |
| Storage | −65 to +150°C | Unpowered storage |
No specifications match. Try a parameter name or a unit.
Original package illustrations and reviewed starting footprints; verify the purchased part and assembly rules.
Connections by function
Select a pin for its function, connection guidance and electrical notes.
Adjustment and feedback1 pin
Supply1 pin
Negative output1 pin
Adjustment and feedback1 pin
Supply2 pins
Negative output1 pin
LM337 at a glance
Follow the labeled connections and functional stages
How it works
3 stages · Explore one step at a time
Regulate below ADJ
The feedback loop maintains OUT minus ADJ near −1.25 V.
Set the magnitude
110 Ω from OUT to ADJ and 330 Ω from ADJ to ground give a nominal output magnitude of 5 V.
Provide stable loading
The divider draws about 11.36 mA. Fit the required output capacitor, positive end toward ground, and calculate the pass-stage loss.
Step 1 of 3
LM337 in a circuit
A physical TO-220 package with the correct input tab and capacitor polarity.
Connect it, step by step
Follow the component values and pin connections
Identify the input
The middle lead and metal tab are negative IN; the right lead is OUT.
Set output magnitude
Use 110 Ω OUT-to-ADJ and 330 Ω ADJ-to-ground.
Check capacitor orientation
Connect the positive ends of the input and output tantalum capacitors to the common return.
Inside LM337
The negative-reference control loop inside the regulator body.
Explore the circuit
Select a stage to see its role and connections
Compare the reference
Maintain OUT minus ADJ near −1.25 V.
Control negative-rail current
Adjust the series stage between negative input and output.
Protect the pass device
Current, thermal and safe-area protection constrain abnormal operation.
Selected packageTO-220LM337T/NOPB
Physical connections3 pinsPackage-specific numbering
Reference collection8 tables48 parameters & pin functions
Pin reference
Signal names, electrical functions and connection guidance
Physical pin numbers3 pins
Scroll within the table to see all columns and rows.
| Pin | Signal | Type | Function & connection |
|---|---|---|---|
| ADJ | Floating adjustment terminal | The regulator holds OUTPUT approximately 1.25 V below ADJ.Connection guidanceConnect R1 from OUT to ADJ and R2 from ADJ to the common return. ADJ is not ground. Adjustment current flows into this terminal. | |
| IN | Negative input and metal tab | Accepts a negative supply more negative than the required output. The TO-220 tab and SOT-223 tab 4 are also IN.Connection guidanceConnect −9 V in the example; keep the live input tab isolated from grounded metal. This pin assignment differs from positive LM317/LM350 regulators. | |
| OUT | Regulated negative output | Supplies the load at a controlled negative voltage relative to the common return.Connection guidanceConnect R1, the load and the required output capacitor here. Polarized output capacitors have their positive end at the common return, not at OUT. | |
| IN / TAB | SOT-223 input tab | The broad SOT-223 contact is internally connected to input lead 2.Connection guidanceConnect to the negative input copper and provide an adequate thermal path. This is a separate physical contact on the same IN node; it is not ground. |
No pins match these filters. Try another signal name or reset the filters.
Operating reference
TI LM337-N electrical column
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Nominal output adjustment | −1.25 to −37 V | With adequate differential voltage, loading and cooling |
| TO-220 order range | 0–125°C junction | LM337T/NOPB |
| SOT-223 order range | −40–125°C junction | LM337IMP/NOPB; do not extend the 0–125°C electrical table implicitly |
| Reference at 25°C | −1.213 / −1.25 / −1.287 V | Manufacturer MIN / TYP / MAX signed entries |
| Reference over stated LM337-N range | −1.20 / −1.25 / −1.30 V | 0–125°C; stated differential and load conditions |
| Adjustment-pin current | 65 µA typical; 100 µA maximum | Flows into ADJ |
| Adjustment current change | 2 µA typical; 5 µA maximum | 10 mA–IMAX; 3–40 V differential; 25°C |
No specifications match. Try a parameter name or a unit.
Electrical test baseline: 5 V input-output differential and 0.5 A load for TO-220/SOT-223, unless specified. Observe the source power conditions.
Regulation and noise
Constant-junction pulse measurements
Manufacturer-referenced values8 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Line regulation at 25°C | 0.01%/V typical; 0.04%/V maximum | 3–40 V differential; 10 mA load |
| Line regulation over stated range | 0.02%/V typical; 0.07%/V maximum | 3–40 V differential |
| Load regulation at 25°C | 0.3% typical; 1% maximum | 10 mA–IMAX |
| Load regulation over stated range | 0.3% typical; 1.5% maximum | Constant-junction test conditions |
| Thermal regulation | 0.003%/W typical; 0.04%/W maximum | 10 ms pulse; 25°C |
| Ripple rejection without CADJ | 60 dB typical | −10 V output; 120 Hz |
| Ripple rejection with 10 µF CADJ | 66 dB minimum; 77 dB typical | −10 V output; 120 Hz |
| Output noise | 0.003% of output typical | RMS; 10 Hz–10 kHz; 25°C |
No specifications match. Try a parameter name or a unit.
Typical values are not guaranteed extremes.
Minimum load and current limiting
Current capability depends on voltage drop
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Minimum load at ≤40 V differential | 2.5 mA typical; 10 mA maximum | Guarantee minimum current to maintain regulation |
| Minimum load at ≤10 V differential | 1.5 mA typical; 6 mA maximum | Manufacturer test condition |
| Current limit at ≤15 V differential | 1.5 / 2.2 / 3.7 A | Minimum / typical / maximum; DCY and NDE within power limits |
| Current limit at 40 V differential | 0.15 A minimum; 0.4 A typical | 25°C; safe-area limit reduces available current |
| Example divider | 1.25 / 110 ≈11.36 mA | Contributes to total output current |
| Divider lower bound | 1.20 / 111.1 ≈10.80 mA | 110 Ω at +1% and 1.20 V reference magnitude |
No specifications match. Try a parameter name or a unit.
A 1.5 A class regulator cannot supply full current at every differential voltage or without cooling.
Capacitors and polarity
Negative rails reverse the polarized capacitor orientation
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Required output capacitor | 1 µF solid tantalum or 10 µF aluminum electrolytic | Required for stability; close to OUT and return |
| Input bypass | 1 µF solid tantalum | Required if more than 4 inches from the supply filter; used locally here |
| Positive capacitor terminals | Common return / GND | Negative ends connect to negative IN or OUT |
| Optional adjustment bypass | Improves ripple rejection | Evaluate discharge protection when added |
| Output discharge diode | Review when CL exceeds 20 µF | Source protection circuit diverts discharge during input short |
| Adjustment discharge diode | Review with CADJ >10 µF and output magnitude >25 V | Follow the source protection circuit |
| Example output capacitor | 1 µF solid tantalum, suitably voltage-rated | An arbitrary ceramic substitute is not assumed |
No specifications match. Try a parameter name or a unit.
The common return is the more positive node in this circuit.
Heat and the input tab
Manufacturer thermal metrics · mounting matters
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 θJA reference | 22.9°C/W | SNVS778F test-board metric; not a universal bare-package value |
| SOT-223 θJA reference | 58.3°C/W | Board copper and mounting strongly affect actual results |
| TO-220 θJC(bottom) | 1°C/W | Manufacturer package metric |
| Live tab | IN in both packages | SOT-223 contact 4 is connected to pin 2 |
| Nominal pass loss | (9 − 5) × (0.100 + 0.01136) ≈0.445 W | At 100 mA load plus divider |
| Absolute differential limit | 40 V | Stress limit; use operating headroom and power constraints |
| Internal protection | Current, thermal and safe-area limiting | Not a substitute for normal thermal design |
No specifications match. Try a parameter name or a unit.
Use the correct case/interface/heatsink or board model when estimating junction temperature.
A nominal −5 V supply
−9 V input · 110 Ω / 330 Ω divider
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| R1 from OUT3 to ADJ1 | 110 Ω, 1% | Divider current about 11.36 mA |
| R2 from ADJ1 to GND | 330 Ω, 1% | R2/R1 = 3 |
| Ideal output | −1.25 × (1 + 330/110) = −5.00 V | Before adjustment current and tolerance |
| Typical IADJ correction | −65 µA × 330 Ω = −21.45 mV | Nominal result approximately −5.021 V |
| Load | 50 Ω, at least 1 W | Between GND and OUT; about 100 mA / 0.5 W |
| Input headroom | Approximately 4 V magnitude | −9 V input, −5 V output |
| Common return | Supply return, R2, load and capacitor positive ends | No dedicated ground pin on the IC |
No specifications match. Try a parameter name or a unit.
Nominal calculations; verify the actual loaded voltage and temperatures.
Physical package reference
LM337T/NOPB · TO-220
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 front-view lead order | 1 ADJ; 2 IN; 3 OUT | Marking toward you; leads down |
| SOT-223 top-view contacts | 1 ADJ; 2 IN; 3 OUT; 4 IN tab | Three narrow leads opposite a broad input tab |
| Selected pitch | 2.54 mm | See physical pin map and footprint |
| Selected operating range | 0–125°C operating junction; tab = IN | Package-specific note |
| Output versus tab | OUT is pin 3; tab is IN | Do not use a positive-regulator tab assumption |
| Storage | −65 to +150°C | Unpowered storage |
No specifications match. Try a parameter name or a unit.
Original package illustrations and reviewed starting footprints; verify the purchased part and assembly rules.
No matching rowsTry a pin name, parameter, unit or test condition, or reset the filters.
Negative analog rails
Supply operational amplifiers and analog circuits that require a negative rail.
Manufacturer application guideAdjustable bench supplies
Combine separate positive and negative regulators around a shared return.
Manufacturer application guidePolarity-aware experiments
Study minimum load, feedback, stability capacitors and thermal limits with a modest DC load.
Manufacturer application guideTake it into ProTech
Find LM337 in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech