LM1117 notes

I pulled some LM1117 voltage regulators from a bunch of routers. I want to use them in another project so I knocked together a quick circuit to test them. Here is the basic LM1117 schematic:


And here it is built up, using mostly random parts from my junk bin. R1 is 200Ohm, R2 is a 1K pot in series with a 200Ohm. The cap is 100uF. I should probably also have a cap on the input, but I’m running this from a bench supply and it seems fine.


The LM1117 is used in a number of applications are a jelly bean variable regular, I’ve seen it typically used as a 1.2 or 3.3v regulator. There’s an interesting application note on this application here.

You can find the datasheet, and some design notes for this part at the end of the post here were it’s used in a RT3050 PCB I was reverse engineering as a 3.3v regulator.