# Help with RC circuit

Discussion in 'Homework Help' started by shiney, Oct 10, 2012.

1. ### shiney Thread Starter New Member

Sep 24, 2012
2
0
hello!

I need some help getting the transfer function for this circuit:

There is no connection in the middle. (where R1 and R2 meet)

I think I know how to get the transfer function if someone can give me some advice how i should get an equivalent impedance transform. Im getting nowhere with this problem without it.

R1=8k
R2=R3=12k
C=100nF

Thanks for the help in advance.

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Last edited: Oct 10, 2012
2. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,082
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I think that you should start from redrawing the diagram to more convenient way.

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3. ### shiney Thread Starter New Member

Sep 24, 2012
2
0
Is this correct:

Vout=( $\frac{R3}{R2+R3}$ - $\frac{R1}{C+R1}$ ) * Vin

H(s) = $\frac{Vout(s)}{Vin(s)}$ = $\frac{R3}{R2+R3}$ - $\frac{R1}{1/sC+R1}$ = $\frac{12000}{12000+12000}$ - $\frac{8000}{1/(s*10^-7)+8000}$ = -0,5-8*10^-4s

??

Last edited: Oct 10, 2012
4. ### WBahn Moderator

Mar 31, 2012
19,150
5,177
Other than not carrying your units, it looks like your first equation needs patching (what does it mean to add C and R1? What is the sum of farads and ohms? But it looks like you got sloppy somewhere between your next to last and your last expression. You might want to be a bit more explicit in the steps you took there and, please, use units!