LM138K STMicroelectronics Integrated Circuit (Other) In Stock
The LM138K is an adjustable positive linear voltage regulator from STMicroelectronics capable of sourcing up to 5 A output current. It supports an input-to-output voltage differential from 3 V to 35 V with 0.01%/V line regulation in a TO-3 metal package. Suitable for high-current laboratory power supplies, industrial motor drives, and precision voltage references.
- Manufacturer
- STMicroelectronics
- Package
- Other
- Pin Count
- 2
- Lifecycle
- OBSOLETE
- Datasheet
- LM138K Datasheet PDF
- Category
- Integrated Circuit
- Price
- From $12.1500(MOQ 1)
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of LM138K?
- Adjustable output voltage set by two external resistors
- Up to 5 A continuous output current for high-current regulated power supplies
- Input-to-output differential range: 3 V to 35 V for flexible design margin
- Line regulation of 0.01%/V for precision voltage stability
- TO-3 metal package with bolt-down thermal mounting for high power dissipation
- Dropout voltage of 3 V minimizing wasted headroom
What is LM138K used for?
The LM138K is designed for high-current adjustable linear power supply applications in laboratory bench supplies, industrial automation equipment, and precision test instruments where low output noise and tight regulation are more important than efficiency. Its 5 A current capability and TO-3 package make it ideal for powering analog signal chains, reference voltage circuits, and motor pre-drivers that require a clean, stable supply rail. The 35 V maximum differential allows operation from unregulated transformer-rectified inputs common in legacy industrial designs.
What are the specifications of LM138K?
| Pbfree Code | Yes |
| Reach Compliance Code | Not Compliant |
| YTEOL | 0 |
| Adjustability | ADJUSTABLE |
| Dropout Voltage1-Nom | 3V |
| Input-Output Voltage Differential-Max | 35V |
| Input-Output Voltage Differential-Min | 3V |
| JESD-30 Code | O-MBFM-P2 |
| JESD-609 Code | e3 |
| Line Regulation-Max (%/V) | 0.01 |
| Load Regulation-Max(%) | 0.3% |
| Number of Functions | 1 |
| Number of Outputs | 1 |
| Operating Temperature TJ-Max | 150°C |
| Operating Temperature TJ-Min | -55 °C |
| Output Current1-Max | 5A |
| Output Voltage1-Max | 32V |
| Output Voltage1-Min | 1.2V |
| Package Body Material | METAL |
| Package Equivalence Code | TO-204/-3 |
| Package Shape | ROUND |
| Package Style | FLANGE MOUNT |
| Qualification Status | Not Qualified |
| Regulator Type | ADJUSTABLE POSITIVE SINGLE OUTPUT STANDARD REGULATOR |
| Surface Mount | NO |
| Technology | BIPOLAR |
| Terminal Finish | MATTE TIN |
| Terminal Form | PIN/PEG |
| Terminal Position | BOTTOM |
| Package | Other |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| ECCN | EAR99 |
| HTS Code | 8542.39.00.60 |
Where can I find the LM138K datasheet?
LM138K Datasheet DownloadOfficial datasheet from STMicroelectronics
What are equivalent replacements for LM138K?
No known alternates. Submit an RFQ and our team can suggest alternatives.
Frequently Asked Questions
How much output current can the LM138K supply, and how does that compare to the LM317?
The LM138K delivers up to 5 A continuous output current, which is five times the 1 A rating of the standard LM317, making it suitable for powering heavy loads such as analog amplifier stages, relay banks, or multiple parallel circuits that would otherwise require paralleled LM317 devices and current-sharing resistors.
What input-to-output voltage differential range does the LM138K support, and why does it matter for transformer-based designs?
The LM138K operates with an input-to-output differential between 3 V and 35 V, meaning the unregulated rectified input can range from 3 V above the desired output up to 35 V higher, giving designers sufficient headroom to absorb mains voltage variations of ±10% while keeping the device within its safe operating area across the full output voltage adjustment range.
What thermal considerations apply when mounting the LM138K TO-3 package for a 5 A load?
At 5 A with a 5 V dropout, the LM138K dissipates 25 W, which requires a heatsink with thermal resistance below approximately 3°C/W to keep junction temperature under 125°C at a 50°C ambient — the TO-3 metal case bolts directly to an aluminum heatsink, achieving junction-to-case thermal resistance of about 4°C/W.
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Why Buy from FindMyChip
About STMicroelectronics
STMicroelectronics is a global semiconductor leader serving customers across the spectrum of electronics applications. ST's products are found in a wide range of applications including automotive, industrial, personal electronics, and communications.
| Qty. | Unit Price | Ext. Price |
|---|---|---|
| 1+ | $16.2500 | $16.25 |
| 25+ | $13.2000 | $330.00 |
| 50+ | $12.6000 | $630.00 |
| 100+ | $12.1500 | $1215.00 |
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