Just a thought.

[Martin Czech]

>      Is it possible to have a band pass filter act as a lp or hp filter.  
> I was thinking I could drop the input signal frequency, run it through 
> the filter, the raise it back up the same amount.  This would be the low 
> pass.  Has this been done, or is it too far off-base?
> Maybe the filter would not be able to span the entire Freq range.
> Any thoughts?  Thanks.
> 
> PS
> 
I can't see how your proposal will work.

Why note use a state var filter? hp. lp. bp notch at the same time.

m.c.