[sdiy] Sallen-Key math question

[John L Marshall]

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.
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> >
> > -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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>