# butterworth filter

Discussion in 'Homework Help' started by josh007, Sep 20, 2015.

1. ### josh007 Thread Starter Member

Sep 20, 2015
40
1
Hi. Help Please. I need the experts to please verify my solution thanks.

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2. ### Papabravo Expert

Feb 24, 2006
10,681
1,983
For starters, I don't think your transfer function represents a Butterworth Filter. Why do you think it does?
Also -- what is with the negative resistance? No passive component is capable of having such a behavior.

josh007 likes this.
3. ### josh007 Thread Starter Member

Sep 20, 2015
40
1
Hi Sir. Please can you advise me on what needs to be done. I just feel like giving up on this subject. I need help please. Please guide me.

I thought to make it look like a third order butterworth filter. Where can I find info that will help me to answer this.

thanks

4. ### recklessrog Member

May 23, 2013
405
130

Go to www.nuhertz.com and download filter free 2012, very useful free software

5. ### Papabravo Expert

Feb 24, 2006
10,681
1,983
I think you might want to start with an expression for Zin(s). Hint: your schematic looks like the equivalent circuit for an active device. The diamond symbol with the arrow inside "looks like" a current source, but with a value of 2V1, it has the wrong units. If instead it is a voltage source, then you have an amplifier with a gain of 2. Knowing what that symbol represents would be most helpful.

6. ### josh007 Thread Starter Member

Sep 20, 2015
40
1
Hi sir. This is the solution that I have derived. Is this correct? I really am battling with this subject. Thanks.

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7. ### Papabravo Expert

Feb 24, 2006
10,681
1,983
The picture of your work is very difficult to read, especially the subscripts, and the drawing is not labeled. So I don't know what the quantities refer to. Try not to take pictures of a page on an angle it hurts my eyes to try and read it.

Isn't
$Z_{in}(s) = \frac{1}{1+2s}|_ {\scriptsize s=j\omega}$

Last edited: Sep 21, 2015