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I am trying to calculate input impedence of a MFB low pass filter. What I need is the symbolic expression as simple as possible so that later I fill in the values and get the impedence itself:

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I am not sure if I am on the right track...specially about the current directions I choosed. would somone kindly verify the steps?

What I need obviously is a simple equation with no current in it!

enter image description here

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I always hated these stuff ....:) – xsari3x Feb 12 '12 at 11:57
what's the reason of "-i3" ? – xsari3x Feb 12 '12 at 12:06
Actually for no particular reason, I just felt lucky to put i3 like tha, it can be +i3 as well...does it matter? – Sean87 Feb 12 '12 at 12:49
how come there is 2 i3 ? – xsari3x Feb 12 '12 at 12:57
1  
See my answer at math.stackexchange.com/a/108866/18398 – Joel Reyes Noche Feb 13 '12 at 13:02
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closed as off topic by Kevin Vermeer Feb 28 '12 at 18:02

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