AMS1117 vs LM317: Which Voltage Regulator to Choose?
By Kunkune | Published: 2026-10-23
Category: Comparisons
Compare the AMS1117 3.3V fixed regulator and the LM317 adjustable regulator. Learn their key differences, trade-offs, and which one fits your project.
Quick answer
Choose the AMS1117 3.3V regulator for a simple, fixed 3.3V output in compact projects. Choose the LM317 adjustable regulator when you need a variable output voltage or higher output current.
Fixed vs adjustable output
The AMS1117 3.3V module delivers a precise 3.3V output without external resistors, making it ideal for powering 3.3V logic, sensors, and microcontrollers. The LM317, on the other hand, requires two external resistors to set the output voltage anywhere from 1.25V to 37V, offering flexibility at the cost of extra components.
Current and thermal considerations
Both are linear regulators, so any voltage drop is dissipated as heat. The AMS1117 is rated for up to 1A, while the LM317 can handle up to 1.5A. For higher current draws or large input-to-output voltage differences, you may need a heatsink. Neither part includes thermal specifications in the supplied catalog data, so check the datasheet for your specific load conditions.
Trade-offs at a glance
- AMS1117 3.3V – Fixed output, simple setup: No external resistors needed. Drop-in replacement for 3.3V rails. Output is fixed at 3.3V. Best when your load requires exactly 3.3V and you want the smallest footprint.
- LM317 – Adjustable output, more flexibility: Requires two external resistors to set the voltage. Can output from 1.25V to 37V. Higher current capability (1.5A). Ideal if you need a voltage other than 3.3V or plan to reuse the regulator in different projects.
- TL431A – Not a direct alternative: The TL431A is a shunt regulator / voltage reference, not a series linear regulator. It cannot source current like the AMS1117 or LM317. Use TL431A when you need a precision reference or shunt regulation, not for powering loads directly.
Product facts
- AMS1117 3.3V Power Supply Step Down Voltage Regulator: The AMS1117 3.3V Power Supply Module is a compact, efficient solution for providing a stable 3.3V output. You can drop it into a 5V or higher rail and get a clean 3.3V supply with minimal external parts, perfect for breadboard or PCB projects.
AMS1117 3.3V Power Supply Step Down Voltage Regulator - 10pcs LM317T Linear Voltage Regulator Adjustable: LM317T Linear Voltage Regulator, Adjustable. You can set any output voltage between 1.25V and 37V with two resistors, making it a versatile choice for prototyping or non-standard voltages.
10pcs LM317T Linear Voltage Regulator Adjustable
Which one fits your project?
Best for
- Projects that need a fixed 3.3V supply with minimal components (AMS1117)
- Prototyping or designs requiring adjustable output voltages up to 37V (LM317)
Not for
- High-efficiency battery-powered designs (linear regulators waste voltage drop as heat)
- Applications needing a precision voltage reference (consider TL431A instead)
