Hello there, I’m just an electronic hobbyist. So I read the LM2940 datasheet and know that I need two capacitors, one on the input and one on the output. They must also be rated higher than my voltages as well.
Now I’m confused about ESR and capacitor type, how to choose them?
Because ESR isn’t listed on data sheets, at least not on the ones I’m looking at.
Btw do you guys have any more specific introduction to LM2940, all I can found on the internet which introduces it more in details is this article:A Comprehensive Introduction to LM2940, but it doesn’t have the answer to my question.
Thank you in advance.
That’s a really complicated question mate 
I’m one of the resident EEs and I can probably help. First off if you want more information about different types of capacitors and their use properties check out this article
Here’s the diagram in the datasheet. There’s also a section 8 that deals with this issue:
Basically you want a ceramic capacitor with an ESR between 0.1 and 1 ohm that is stable over a wide temperature range. Unfortunately 22uF is near the upper limit of where the industry makes multi-layer ceramic capacitors (MLCC). You’ll probably be able to find one, it will just take a minute to filter correctly.
The classic “big” capacitors are the can shaped Electrolytic capacitors, but their ESR is far too high for this use case. The other option is to use a tantalum capacitor, but you have to be very careful specc’ing those out because they’re whacky and often application specific.
If you’re having trouble finding a low ESR 22uF MLCC let us know and someone can give you a few example links.
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