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three stage RC low pass filter ct off frequency expression (Read 2839 times)

singh Community Member Offline Posts: 57	three stage RC low pass filter ct off frequency expression Nov 18^th, 2011, 4:39am can anyone help me with the cutoff frequency for third order passive low pass filter with three stage RC filter circuit.i tried to derive it but its very very compex transfer function. Please let me know any reference of the cut off frequency expression for three stage low pass RC filter.
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: three stage RC low pass filter ct off frequency expression Reply #1 - Nov 18^th, 2011, 6:22am hello, For a passive ckt you dont get complex poles, because there is no chance of ringing. So i am sure some thing is wrong. But you can estimate appoxematly the following. Thanks, Raj.
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loose-electron

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Re: three stage RC low pass filter ct off frequency expression
Reply #2 - Nov 18^th, 2011, 9:17am

three mesh equations to get the current in the last capacitor.

Or, do Thevin to Norton conversions starting at the input sources until you get to the output load. End result is one complex impedance in parallel with a current source. (Laplace transformations for the impedances)

It's tedious, but can be done.

Jerry Twomey
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