# help please on deriving transfer functon

Discussion in 'Homework Help' started by BuMalak, Oct 19, 2012.

1. ### BuMalak Thread Starter New Member

Oct 12, 2012
17
0
hi everyone,

Note: the capacitors are not the same

Thank you

2. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,301
339
Did you read the sticky at the top of the forum?

You need to show some effort to solve the problem before anyone will help you.

If the two capacitors are not the same, then you should label them differently, perhaps C1 and C2.

BuMalak likes this.

Oct 12, 2012
17
0
Ok I will.

Thank you

4. ### BuMalak Thread Starter New Member

Oct 12, 2012
17
0
This is what I found:

(0.01s^2 + 10s ) / 10^-9*s^3 + 0.02s^2 + 20s +1

5. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,301
339
It is not possible to verify if you don't tell us the value of the resistors and capacitors.

Suppose your result is incorrect; wouldn't you like to know where your mistake is? If you only give a final result but don't show your work, nobody can help you.

6. ### BuMalak Thread Starter New Member

Oct 12, 2012
17
0
R1=R2=R3=10kohm
C1=C2=0.1uF

7. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,301
339
This is not correct. Your denominator is a 3rd order polynomial, but your circuit only has two capacitors (I assmume the opamp is ideal).

Have a look here:

http://sim.okawa-denshi.jp/en/OPtazyuBakeisan.htm

If you'll show your work, we can see where you went wrong.

8. ### BuMalak Thread Starter New Member

Oct 12, 2012
17
0
It is difficult for me to write down all my steps here ><
but, you actually helped me and I figured out my mistake.

Thank you very much

9. ### blah2222 Well-Known Member

May 3, 2010
565
33
Also for next time, a clear way to present your math is to use LaTeX formatting.

Instead of having everything look like this:

H(s) = (2s^2 + 3s + 1)/(4s + 2)

Use LaTeX to get this:

$
H(s) = \frac{2s^{2} + 3s + 1}{4s + 2}
$

Here's the link to other functions for LaTeX. Quote this message to see how it works:

http://www.access2science.com/latex/Functions.html