Noob wants to know: How does gain work?

[frank_p]

The more negative feedback is applied, the harder you are stepping on the brakes.

Good analogy, Mark.  Gimme a physical model over maths any day.

Well of course it was good.  I just figured that if someone not so mathematically inclined wanted to understand the same concepts, I'd tackle it another way.  Even the hopelessly naive and underinformed deserve an explanation!

And Mech. E. guys too,     
A hot-rodded Chevy without brakes is like is like a "boutique" TS without negative feedback.  And a hot-rod without pedals is like Stompbox without stompswitch.

http://uncyclopedia.org/wiki/Feedback

Oh !  Just as I was typing that post I got My Art of Electronics by the mailman !  It's a sign... 

[sprog]

Even the hopelessly naive and underinformed deserve an explanation!

What are you saying, Mark? 


  Just Kidding! I for one really appreciate all of your posts here & would still be trying to figure out how to get the bottom plates off of my pedals if it weren't for your shared wisdom. I know I'm barely above the troglodyte level, but some day I'll be cooking with fire!

c'mon my mathematical explanation was pretty good.. even I understood it!!!

I'm still groping around for a handle on the math part, but rest assured that I will figure it out thanks in part to your explanation. I'll do it the same way one eats an elephant.... one bite at a time.



Truthfully, I appreciate everyone who takes the time & effort to help me & other rookies like me who couldn't find their butt even if it had a bell on it. It sure minimizes the learning curve. I also appreciate not being told to use the 'search' button every time I have a question - I do that anyway, but sometimes when you're green you don't even know how to ask the right question(s). Anyway, thanks everbody!

[Mark Hammer]

I learned from some of the best.

Years ago, through a fluke, I ended up sitting beside the late astrophysicist Carl "Billions and billions of stars" Sagan.  I asked him how it was possible to conceive of the distance between astral bodies.  His reply was that eventually you start to think of it like a neighbourhood.  Instead of "Drive for two blocks and turn left at the Shell station", it's "Go straight out until you reach Alpha Centauri and hang a left.  You can't miss it.".  Generally speaking, people learn complex ideas by seeing their resemblance to the familiar, so that's often where useful explanations start.  Renowned intelligence theorist Robert Sternberg has a delightful teaching and speaking style that I've had the pleasure to witness firsthand on several occasions.  No matter how sophisticated and arcane the subject matter, he always starts with an everyday analogy that makes sense to absolutely everyone in the room.  Once people accept that they already understand a great deal about the phenomenon to be discussed at an intuitive level, then he begins to ramp up the detail and use of more technical language.

In two more nights, it will be Passover (and believe it or not, that IS my middle name).  During the traditional Seder meal, the story is told of the 4 very different sons who ask about the rituals and meaning of the holiday.  Well, three sons to be precise.  The 4th is described as not even knowing enough to ask the question.  Still, we are told, THAT son deserves an explanation every bit as much as the others.  That part has always been meaningful to me, and in the years when I was teaching, I made it a point to take care of "the 4th son".  There are those whose poverty consists of what is not in their stomachs, and there are those whose poverty consists of what is not in their thoughts or understanding.  They are hungry in another way.  You have to take care of all the poor, those who want to feel full in their bellies for a change, and those who want to feel full in their understanding.  For me, tweaking an explanation so that those who feel outside the circle can now feel part of the community is not much different than dropping cans off in the food bank hamper.

[frank_p]

Not in the opamp topic, but this analogy is one of my favorites (because it works in calculations also).




Ref:  http://www.lightandmatter.com/html_books/4em/ch07/ch07.html

At first it might seem "rude" but you can meditate a long time on this one.    Analogies are useful for knowing what is similar and what is different.  Similar vs different gets you to better understanding of the "ways of nature" vs science.  Models vs what is real and understandable by knowledge.

[dschwartz]

and IMHO, the capability to make analogies is a reflect of a very powerful mind...

i was thrilled with my explanation cause the only thing i knew about opamps till yesterday, was that they have thee + and - input and they compare (substract) both inputs,  And  the formulas for calculating gain..
So while i was writing the explanation, the infamous "WHY" quistion bugged me and started to make those ugly equations..i was so thrilled when i demostrated to myself that a buffer has 1 of gain!! and ended up deducing the gain formula only using reasoning..

sometimes, questions like this are truly "pandora´s boxes", cause answering them is a master class for oneself..

[dschwartz]

Not in the opamp topic, but this analogy is one of my favorites (because it works in calculations also).




Ref:  http://www.lightandmatter.com/html_books/4em/ch07/ch07.html

At first it might seem "rude" but you can meditate a long time on this one.    Analogies are useful for knowing what is similar and what is different.  Similar vs different gets you to better understanding of the "ways of nature" vs science.  Models vs what is real and understandable by knowledge.

haha right!! i´ve always though of decoupling caps as a car shock absorbers, being the road´s bumps the noise on the B+