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Design >> Analog Design >> three stage RC low pass filter ct off frequency expression
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Message started by singh on Nov 18^th, 2011, 4:39am

Title: three stage RC low pass filter ct off frequency expression
Post by singh on 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.

Title: Re: three stage RC low pass filter ct off frequency expression
Post by raja.cedt on 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.

Title: Re: three stage RC low pass filter ct off frequency expression
Post by loose-electron on 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.