[sdiy] Sallen-Key math question

[Jim Patchell]

    It is just a different way to write the same thing.  Both expresions will
give the same result.

    -Jim

John L Marshall wrote:

> I going from memory too isn't it Wc=1/SQRT(R1R2C1C2)?
>
> John
>
> ----- Original Message -----
> From: Jim Patchell <patchell at silcom.com>
> To: <music.maker at gte.net>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Sent: Monday, October 15, 2001 10:15 AM
> Subject: Re: [sdiy] Sallen-Key math question
>
> >     If the R's and C's are equal Wc = 1/RC,  If they are not equal then
> > Wc = SQRT(1/R1R2C1C2)
> >
> >     Also note Wc = Fc * 2 * PI
> >
> >     Please note, this was done from memory...
> >
> >     -Jim
> >
> > Scott Gravenhorst wrote:
> >
> > > I keep looking at the math for this filter in the
> > > Lancaster's "Active Filter Cookbook" and frankly,
> > > I just don't get it.  What I'm after is given a
> > > cap of size C and a resistor of R ohms, what is
> > > Fc ?  The diagram clearly shows how to calculate
> > > R for a given Q value, but I don't see how to get
> > > Fc.
> > >
> > > Is there a better source of info for this ?
> > >
> > > NOTE:  I am NOT an EE.
> > >
> > > =========================================================
> > > - Government: The other religion.
> > > - The media's credibility should always be questioned.
> > > - Lambs who lie down with lions are lunch.
> > >
> > > -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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> >