Yes.Has anyone seen something like this in filter design?
Hello, thank you for responding to my post. can you add more to your comment, "for a special case onlye: R3 = R4"? What cases is this not okay?Yes - the given formulas are correct.
The table contains the design parameters for the second-order lowpass in MFB topology - however, for a special case only: R3=R4.
(In some cases, another design strategy may be preferred: Selection of standard capacitor values).
It should be mentioned that the given set of equations can be used not only for Butterworth responses because the parameter α ("coupling factor") is the well-known quality factor Qp (α=Qp) and the frequency ωo is identical to the pole frequency (ωo=ωp). However, only for a Butterworth response the pole frequency is identical to the 3dB cutoff frequency.
These pole parameters are available (tabulated) for Butterworth and Thomson-Bessel reponses as well as a variety of Chebyshev responses and can be found in many documents.
Hi Joe....In principle, there is an infinite number of alternatives for finding/selecting parts values for such a circuit. However, why not simplify formulas and start with some good assumptions? For example: R3=R4......Hello, thank you for responding to my post. can you add more to your comment, "for a special case onlye: R3 = R4"? What cases is this not okay?
No, you must select all the variables and parameters so that the parts values are positiv.Can someone look at the calculations for the Band-pass Negative Feedback the R2 calculation seems to always be negative. Do you take the absolute value of the term?
Hi Joe...."something like this" can be found in many books on filter design. However, for my opinion, the given expressions in the tables are nor easy to interpret and - more than that - they are restricted to one parameter set only.Hello, my co-worker gave me the a quick guide for filter design.
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Has anyone seen something like this in filter design? I've working the numbers to see if it is valid.
Thank you very much. I will visit TI's web site.
by Gary Elinoff
by Robert Keim