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

Discussion in 'Homework Help' started by tim_3491, Apr 20, 2008.

1. ### tim_3491 Thread Starter New Member

Apr 1, 2008
7
0
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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2. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Check out section 16.5.1.1 in this document on opamps. It has the final answer

hgmjr

3. ### scubasteve_911 Senior Member

Dec 27, 2007
1,202
1
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

4. ### Caveman Active Member

Apr 15, 2008
471
0
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."

5. ### tim_3491 Thread Starter New Member

Apr 1, 2008
7
0
I will use the document you have provided, hopefully it will work, thanks for your help