ODP: 6-pole switched capacitor filter "Q's" (literally)

[Roman Sowa]

Just thinging loud...

Guess this filter is inverting phase by 180 deg just above
cutoff frequency. So if you invert its output once again
and feed its input with it, I say it would be resonant at that frequency.

And I don't see why it should freak out just because it is SC filter.
but anyway I'd put simple RC at output.

Roman

> -----Oryginalna wiadomość-----
> Od:	Duane R Balvage [SMTP:dbalvage at ptdcs2.ra.intel.com]
> Wysłano:	31 grudnia 1998 22:38
> Do:	Synth-DIY
> Temat:	6-pole switched capacitor filter "Q's" (literally)
> 
> Hello all -
> 
> I have ordered some switched cap 6-pole butterworth filter chips from
> National Semi... I originally got them to replace the anti-aliasing
> filter and reconstruction filter in my Prophet-2000 sampler, but I got a
> (strange) idea...
> 
> Can you loop the output through a VCA or variable attenuator back to the
> input for a resonance control? Or will the switched-cap filter freeak
> out if you do that? Anyone tried this? I don't have the chips yet, but I
> was thinking of trying this.
> 
> 				- Duane
> -- 
>    "That boy's got a mouth like a cannon ... Always shootin' it off..."
>                                 
>                              - Foghorn Leghorn
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