Hi David,

On 3/20/2011 3:54 PM, David Nebenzahl wrote:
On 3/19/2011 11:51 PM D Yuniskis spake thus:

On 3/19/2011 6:39 PM, David Nebenzahl wrote:

I'm looking for an online electronics forum (web-based) where I can post
some questions.

I think you have to refine your overall goals/interests.
There are many places you can find out "how to use an op amp"
(or, "how an op amp works", etc.).

But, what you *want* to use that op amp for is probably where
you will get far more pertinent information/advice if you can
refine your needs better.

Be that as it may, I went ahead and joined the first forum that was
suggested here (Electro-Tech Online, http://www.electro-tech-online.com)
and whaddya know, I got answers--pretty good ones--within an hour that
allowed me to get parts of my project working. Maybe it's not the

Great! Then you're set -- for now.

definitive, be-all and end-all of understanding op amp operation that

No, quite the contrary. If you know *everything* about op amps,
then there is no difference between applications -- because you
already know all the little details that differentiate one
type of application from another.

My point was, if you find a group that is dealing with the same
types of applications that you are wanting to address, then they
will have already tweaked the "oversimplification" of what an
op amp is by appending "... except, you have to do ________ when
you use it *this* way _______" to that description. I.e., they
will have highlighted the details that are important in *that*
type of application (e.g., if you are running with a single
supply instead of balanced supplies, needing more voltage
compliance in your output than the op amp can provide, etc.)

Most of "design" is figuring out which details to *ignore* and
which to *pursue*. A group of folks working on similar
applications will have already sorted that out for you.

[I recall designing (passive) speaker crossover networks with
a friend at school. He always had "50 ..." as his expressions.
I finally asked him where the heck he kept coming up with this
"50"?? Ans: 2 * pi * 8 ohms (more or less)

D'oh!

you seem to be suggesting, but that isn't what I asked for anyhow. I'm
just trying to muddle through at this point.

Actually, I have a pretty good textbook which probably has all the
answers I need, if I can only understand them: Albert Malvino's
/Electronic Principles/ (actually fished out of a dumpster!). It's
extremely well-written and explains all about op amp operation,
including the four feedback configurations (SP/SS/PP/PS), calculating
gain and impedance, and various op amp applications. Now if I can only
get over having to deal with the math (ugh!) ...

I started with Senturia & Wedlock's _Electronic Circuits and
Applications_ (and, before that, just reading data sheets). It
was one of those "good" books that predated the "sold by the
pound" trend that seems to have infected "modern" writing :
(though it was $20+ about 35 years ago!)

There also were "Made Simple" books aeons ago (When Dinosaurs
Walked the Earth). These were the precursors of the "For Dummies"
books -- but infinitely more intense! Highly condensed but
very good to get exposed to a lot in very few pages.
(e.g., "Electronics Made Simple")