An application note is essentially a document a (typically semiconductor) company puts out in order to demonstrate the capabilities of their hardware by giving examples of how to use their components.
However, not all of them are for marketing purposes. Some of them contain general engineering principles and insights you'd learn only after years of industry experience. These types of notes are often the most valuable due to the broadness of their application.
Quality varies substantially from company to company and depends heavily on the author. Appeal to authority is very real here, so much so that there are extremely famous AN authors such as the late Jim Williams who wrote troves of extremely valuable documents throughout his entire career.
Besides these, this page also has whitepapers, presentations, websites, and different research papers that are of interest.
Goes over different types of oscilloscopes and how they work. Very insightful look at one of the most important instruments in our discipline
Has a plethora of example op amp circuits. Don't expect to learn the "how" of the circuits though
Much less of a "note" and more of an e-book. Goes over pretty much everything you need to know about op amps. I find this more approachable than a dedicated electronics book
The title is much longer, but it is very descriptive in regards to the subject matter. This is very useful for the realization of circuits and is something they seldom teach in school. At least for me :(
More about op amps from TI. Seems to be a theme at that company. I must admit, I did not spend long reading through this "report" as they call it. No matter the fact, its still a good resource from what I can gather at a glance
Title says it all, very useful for RF design engineers
While at a glance this may seem like one gigantic datasheet, the real gems lie in the test circuit figures
This offers no academic or professional value. This is just really funny
Superb. If this topic interests you, read it
Goes through S parameters all the way to broadband LNA design. Very impressive in only 44 pages. Is this a testament to the author's knowledge or textbook author's long-windedness?
From what I garnered, it has the same material as above but in presentation format. More digestible for those of us with shorter attention spans, such as myself
This is exactly the same as AN-95-1. However it is in a report format rather than presentation
Gives a small briefing on basic antenna theory for the first half. The second half is a bunch of reference designs. I like replicating the designs in a tool like openEMS
Excellent design resource for actually integrating an antenna into a system