Jim Williams App Notes

I have been thinking about other categories on the CE forum, and I think there might eventually be an “App Note” section. It had me thinking about the late, great Jim Williams (RIP) who was the lead Application Engineer at Linear Tech (also, RIP). Here is Kent Lundberg’s list of greatest app notes, which is a great recap of the really good ones:

A word of caution :This is a rabbit hole

If you’re not well versed in electronics, you will likely not understand a large portion of these notes. Hell, I’ve been in it 10+ years and I still don’t. JW was one of the best out there. But sometimes it’s nice to see what is possible over time.

I’ll keep cogitating on whether we should have an app-note category.


Hunh, some of those links are broken. Just search for “Linear Tech App Note 25” and it should come up on Google with this link:

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If we’re pretty new here, how much should we be expected to understand? That was a lot of stuff I don’t understand. I think I’ve seen switching regulators in reviews before, but it never had that many components, it always was a couple of small components with a square in the middle (that I assume is doing some kind of control?)

I mean even a lot of this circuit I still have trouble understanding:

I’d say beginners should focus on identifying components in any new schematic they see. After that, start to visualize where the current might be flowing in the circuit (for instance: how much current is likely flowing into Vin?). This one is tough because there are feedback loops as well, which is another layer of complexity. Do your best to read through some of the prose and see if you can understand what is being said. For as much in-depth content JW writes about, I always thought he did a great job explaining it.

So i’ve been thinking about capacitors a bunch lately, so my eyes were drawn to those. Why do some have plus symbols and the one in the upper right has two stars next to it? I can identifiy capacitors but those make it confusing.

The plus sign just means that it is a polarized capacitor. In this case it is most likely to be an electrolytic. In other circuits, you might see the same thing on a tantalum. This is just standard electronics notation.

The two asterisks just identify a note. If you look at the bottom left of the schematic, you’ll see the same marks with a part number next to it. While this isn’t quite standard, you see notes like this a lot on larger schematics.

Martin Jay McKee

Thanks Martin! To add to this, you’ll probably see this less and less @United12. Most things we’re working with these days are ceramic capacitors, which aren’t normally polarized. However, if you see a polarization symbol on a schematic or board…pay close attention. Failing to do so can result in blown caps.

Absolutely wonderful. I am a big fan of Jim Williams and Bob Paese.
Thanks for the collection, I will certainly browse through it.

Umm, yes, but it is our purpose in life to learn, is it not?
You are right, it does take an effort to really understand what is going on. But hey, who cares if you have to chew on one of those application notes for three days. It will shine in the end.


Too right! It’s worth looking through and getting a feel for what’s out there.


Exactly that! Learning is one aspect, the other is being aware of what you don’t know.

If I don’t understand something I keep coming back to it from time to time. It’s amazing what your brain will piece together during the ‘away time’.

IMO, the key thing is not to give up, or be intimidated by the technical terms and mathematics. Most things can be grasped by looking at them from the right angle.