Performing small signal ac analysis with non-linear components
Not too much for me to say since it's so straightforward other than make sure to read through the derivation, especially the parts related to the first two terms of the exponential series.








Source: Microelectronic Circuits 7th Edition, Sedra/Smith

It's a good book, though it can be difficult to tell if you're in class getting so much work shoveled onto you that you never have the chance to actually sit down and read it. The paperback is half the price of hardcover. You should buy it.