Good basic read

[R.G.]

http://www.hills2.u-net.com/op-amp/op-amp.htm

[petemoore]

I'm getting ALot out of it already.
 Glad you brought this one to my attention. Great read.
 I know a good bit about how to work with opamps...even understand the math...sort of...I just can't read, speak or write it ... yet.
 I'd like to use this one as an example of my learned level, citing examples of it for reference, it should give you an idea of where I dwell 'academically'...
 here's one:
 " The output signal voltage of an opamp is proportional to the differential signal voltage and, at low frequencies, is given by:
 e out= Ao[e1-e2] "
 the first equation...I think I almost understand this. Please correct me:
 e out ... means output, why labeled 'e'
 = ... means equal
 Ao means opamp output
 {  ... means I don't know what that means
 e ... he used this letter on the output, must be referring to an input
 1 ... means '+ or _ input'
 -    means subtract
 e2  the second or other input..+ or _
 ]  ...indicates the end of the 'sub-equation'...I don't know what to do with what's in a paragraph [mulitply/divide.?.etc.], this set of the equation is to be done first ?
 I guess I need math lessons...Grrrr...It wouldn't be so bad if I could 'read, and know what the equation characters were intended to represent.
 Some how I've managed to 'sponge' my way along...if there were a page...such as this...but had highlighted letters as buttons to reveal subtext reference pages that...[to analygize]...give an 'exploded view', and further break down to give 'dimensions' for each component...
 I know this is a long typing process I'm asking for,..am I alone ?...if there's a page or articles somewhere that has the 'Emath' reference texts I need to understand this article...that would be easier than bringing equational math lessons to the forum...and de-necessitate long, typed out, math discussions.
 Any help IS greatly appreciated...Thank you !!!
 Every time I read articles such as this I think I almost grasp the formulas...and probably do, because I have exp. working with OA's...but I just can't quite click on how the equation formulas do the OA math, I know I could like it better...I'm still struggling.
 Sometimes I feel I need to 'get educated'

[H.Manback]

I have to say, opamps are very powerful when you understand the principles of positive and negative feedback. However, I do think it's a pretty difficult subject to really understand if you do not take a course in electronics (at school/college/whatever or by self educating).

Practical work with opamp circuits really help tremendously in understanding these concepts. Unfortunately, proper equipment does not come cheap (an oscilloscope is REALLY useful when doing this kind of research).

This link R.G. posted seems to be pretty in depth, haven't read the whole thing, but I hope it doesn't have a steep learning curve. Really useful stuff, especially when your 'library' of cookbook opamp circuits is not that big (read for people like me ).

The eout stuff... I think he just uses e for Voltage or something, since he uses e for inputs as well.

[onboard]

RG, I was just over at GEO to refer to the Electronics Resources section. You're articles are there, and Graham Knott's link is good, but Tom Engdahl's link and the rest at the bottom of the page -  Basics, Measuring, Theory, Design, Component Information, Circuit Board Design, etc. - are down.    Just letting you know (you probably knew that)

I know you're not responsible for maintaing a compendium of the web's electronics resources, but a little link list like that was sure handy. Gotta Google I guess.  (where did all the alliteration suddenly come from?)

The opamp manual is great, thank you for posting the link! There's quite alot of scattered info out there so anytime something comprehensive - and comprehendable - comes along is a very good thing.

edit Here's a link I want to contribute - A Single-Supply Opamp Circuit Collection from TI.

[Paul Marossy]

Someone correct me if I'm wrong, but I believe that Engdahl's site is now called www.epanorama.net

[R.G.]

Every time I read articles such as this I think I almost grasp the formulas...and probably do, because I have exp. working with OA's...but I just can't quite click on how the equation formulas do the OA math, I know I could like it better...I'm still struggling.

It's a foreign language, and learning it is tough. But like all languages, there are some things you can't express adequately in another language.

" The output signal voltage of an opamp is proportional to the differential signal voltage and, at low frequencies, is given by:
e out= Ao[e1-e2] "
the first equation...I think I almost understand this. Please correct me:
e out ... means output, why labeled 'e'

For some reason I never found out, engineering texts use "e" for voltages. Maybe standing for "electrical potential".

= ... means equal

Nailed that one.

Ao means opamp output

No, it means the open loop gain of the opamp. "A" in gain/control theory contexts is used for gain pretty frequently

{ ... means I don't know what that means

There are many symbols used for grouping. Nested parentheses "(..(..))"
get really hard to read after a while. So there are lots of ways to say grouping - like [...]. {...}, <...>, and so on. Sometimes you have to get the grouping from context - which means you have to already know the language.

e ... he used this letter on the output, must be referring to an input

Just to a voltage. Usually the primary variable (the "e" in this case) is differentiated as to *where* it is by a subscript. In this case, the term would be "e subscript "out"" indicating just the voltage at the output.

1 ... means '+ or _ input'

e-subscript-1 means voltage number one

- means subtract

Correct

e2 the second or other input..+ or _

Actually, the voltage at the other input, e-subscript-2.

] ...indicates the end of the 'sub-equation'...
I don't know what to do with what's in a paragraph [mulitply/divide.?.etc.], this set of the equation is to be done first ?

Correct. The stuff grouped inside the brackets is to be calculated first, then the result is to be used as a single number for things outside the brackets.

Math notation also assumes you multiply things written side by side. In this case, the A-subscript-o and the result of subtracting e-subscript-1 and e-subscript-2.

So the way this should read is

The output voltage indicated by e-sub-out is equal to the open loop amplifier gain A-sub-openloop times the difference between input voltages e-sub-1 and e-sub-2.

I wish there was a simple way to do this, but there's really not. It's a combination of algebra notation, calculus notation, and naming conventions from physics (I think that's where the "e" comes from) and control theory. Like any language, it might help to have a pushbutton legend for a set of text, but to really learn to understand the language, you have to dive in and start using and speaking it. And that is **hard**.

[petemoore]

 
 ...I'll keep trying !!! Thanks for the explanation !!!
 If I start 'speaking' I'll probably start typing, and you'll be able to tell whether I got it or not..I learned a couple new rules here at least...I can sort of read it, and a %age of makes sense, but I couldn't verify those numbers or write them... ...I'm gettin' better 1!!  

[Rob Strand]

Pretty good.  Ray Marston used to write articles for electronics magazines in the 80's (like ETI) - usually does a good job of overviewing a subject.

Keep in mind that this stuff is an overview of key points.  The active filters have non-inverting opamps with gain.  That design isn't the best one to choose, the circuits look conceptially simple because of the equal R and C values.