# OP Amp is this correct, and how do i solve.

#### tim_3491

Joined Apr 1, 2008
7
Hi guys

I have attached what i have done so far. Page 3 shows my working and what i need is a function for Vin and Vout. Can anyone see if they can solve the last fraction part on page 3 (problem part)jpeg for me.

Thanks

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#### hgmjr

Joined Jan 28, 2005
9,029
Check out section 16.5.1.1 in this document on opamps. It has the final answer

hgmjr

#### scubasteve_911

Joined Dec 27, 2007
1,203
Why not use Laplace for this? Have you used Laplace circuit analysis in the past? It's a bit easier to work with.

To get your TF, you just isolate the variables of interest on each side, common factor out, then divide.

Steve

#### Caveman

Joined Apr 15, 2008
471
It took me way too long to see it, but you have a math error at the top of your last sheet.
You have I1 + I2 = I3 + I4, which is fine.
But for I4, you have substituted -Vout/4R. Your sign is wrong.
This should be Vout/4R.

Now your answer should jive with the "opamps for everyone" answer on page 16-30. Otherwise, just get the equation to the form Vout/Vin = ... That is your needed answer. Try to put it into the form of the "opamps for everyone."