So, you want to know how opamps work or where they're used?
Either question is easily answerable by Google searches. Off the top of my head I can name a few (tens) of applications of opamps:
- inverting amplifier
- non-inverting amplifier
- voltage adder
- voltage substractor
- comparator
- voltage stabilizer/regulator
- Schmidt trigger
- integrator
- differentiator
- ADCs
- DACs
- oscillators
- instrumentation amplifier
and in many many many other more specific applications.
This is a book that popped up in Google searches about Analog Integrated Circuits (I would give you a link to the course I took in University on the subject but it wouldn't really help because it's in Romanian and it requires a username and password):
"Analog Integrated Circuits" by A.P.Godse and U.A.Bakshi -
http://books.google.com/books?id=txEHUz-0598C&printsec=frontcover#v=onepage&q&f;=false
