No subject

[Robert Pietrusko]

Hi Magnus,

The best reference I have found, and the one I am
using, is the old Van Valkenburg text "Analog Filter
Design," which has been a bible for any other filters
I've designed.  In this case I am using mainly
chapters 12 and 13.

The Gioffi equations in chapter 12 are used to compute
resistor and capacitor values for a Boctor active
filter circuit from a 2nd order transfer function. 
The result is a high-pass notch. I'm fairly certain I
can't get this response out of a Sallen-Key design.

I guess another more practical question is,  if most
people are not familiar with this approach and I am
having a hard time finding material, am I barking up
the wrong tree?

What is a more "standard" method of realizing
Cauer/Elliptic filters using opamps? or even, a more
standard method of realizing high-pass notch functions
that are peaky at the cutoff frequency?

as is  always the case for me, it's not the filter
design, but its analog implementation that is causing
the trouble. :) ugh!

I'd be happy to message in more detail off list to
spare the inboxes of other list members.


-bobby.






From: Robert Pietrusko <bobby at csounds.com>
Subject: [sdiy] new to the list... already have a
question :)
Date: Mon, 29 Dec 2003 19:10:33 -0800 (PST)
Message-ID:
<20031230031033.93100.qmail at web41305.mail.yahoo.com>

> Hi List,

Hi Bobby,

> I'm curious if anyone on the list has experience
> designing Boctor High Pass Notch circuits using the
> Gioffi equations. 
>
> I'm working on a 10th order Cauer filter design
(split
> into second-order-sections which will be designed as
> cascaded high-pass notches) and for all but the
first
> section I am getting negative values for my Rs and
Cs!
> There is an inequality involving Q, Wz and Wo that
my
> coefficients are violating, so I'm sure this has
> something to do with it.
>
> Does anyone know of a workaround? I really need this
> high-pass notch response for my filter (i think) and
> I've been wrestling with it all day.
>
> Thanks in advance for any help you can offer.

Well, excuse me for my ignorance, but do you happend
to have a reference (or
several) to the Boctor/Gioffi material, which I
haven't heard about.

Might I assume you are doing something in Csound or is
this a discrete design?
Additional details like that might help you know.

Cheers,
Magnus