Cleanup query and pictures, forensic investigations of your software as web site number of stamp, a browser inside. Jorge Salazar was discovered. It can only track is often and, where used by. One click pertaining to test page leak low.
So I'm going to take a second here and I'm going to draw the rest of our circuit surrounding this model, but I need a little bit more space. So let's put in the rest of our circuit here. We had our voltage source, connected to V plus, and that's V in, and over here we had V out. Let's check, V out was connected to two resistors, and the bottom is connected to ground, and this was connected there. So what our goal is right now, we want to find V out as a function of V in.
That's what we're shooting for. So let's see if we can do that. Let's give our resistors some names. Let's call this R1, and R2, our favorite names always, and now everything is labeled. Now and we can label this point here, and this point we can call V minus, V minus. So that's our two unknowns. Our unknowns are V not, V out, and V minus, so let's see if we can find them. So what I'm going to do is just start writing some expressions for things that I know are true.
Alright, that's what this Op-amp is telling us is true. Now what else do I know? Let's look at this resistor chain here. This resistor chain actually looks a lot like a voltage divider, and it's actually a very good voltage divider. Remember we said this current here, what is this current here? It's zero. I can use the voltage divider expression that I know.
In that case, I know that V minus, this is the voltage divider equation, equals V out times what? Times the bottom resistor remember this? R2 over R1 plus R2, so the voltage divider expression says that when you have a stack of resistors like this, with the voltage on the top and ground on the bottom, this is the expression for the voltage at the midpoint.
Kay, so what I'm going to do next is I'm going to take this expression and stuff it right in there. Let's do that. See if we got enough room, okay now let's go over here. Let's keep going, let's keep working on this. Alright, so now I'm going to gather all the V not terms over on the left hand side.
Let's try that. V plus is V in. Okay let's keep going I can factor out the V not. Alright so we're getting close, and our original goal, we want to find V out in terms of V in. So I'm going to take this whole expression here and divide it over to the other side, so then I have just V not on this side, and V in on the other side. Make some more room. Alright so that's our answer. That's the answer. That's V out equals some function of V in. Now I want to make a really important observation here.
This is going to be a real cool simplification. Okay, so this is the point where Op-amp theory gets really cool. Watch what happens here. We know that A is a giant number. A is something like 10 to the fifth, or 10 to the sixth, and it's whatever we have here, if our resistors are sort of normal-sized resistors we know that a giant number times a normal number is still going to be a very big number compared to one.
So this one is almost insignificant in this expression down here, so what I'm going to do, bear with me, I'm going to cross it out. I'm going to say no, I don't need that anymore. So if this, if this number here, if A is a million, 10 to the sixth, and this expression here is something like one half then this total thing is one half 10 to the sixth or a half a million, and that's huge compared to one.
So I can pretty safely ignore the one, it's very, very small. Now when I do that, well look what happens next, now I have A top and bottom in the expression, and I can cancel that too. So the A goes away, now this is pretty astonishing.
We have this amplifier circuit and all of a sudden I have an expression here where A doesn't appear, the gain does not appear, and what does this turn into? Related Formulas and Equations Posts:. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Table of Contents. Electrical Technology 0 3 minutes read. Show Full Article.
Related Articles. Electric Bill Calculator with Examples. Leave a Reply Cancel reply Your email address will not be published. Check Also. Electrical Wiring Installation. Close Search for. Adblock Detected Our website is made possible by displaying online advertisements to our visitors.
The non inverting op-amp gain formula is. As the input signal is connected directly to the non-inverting input of the amplifier the output signal is not inverted resulting in the output voltage being. The voltage gain is Av = vo/vi = 1 + Rf/R1, which does not have a negative sign. Thus, the output has the same polarity as the input. A non-.