"Sallen-Key" Public domain?

mashaffer · 23rd July 2008, 10:59 PM

I am trying to understand the Sallen-Key Multiple Feedback 3rd order LP filter well enough to design one from scratch thus I was wondering whether the original S-K paper of 1955 was available in the public domain or whether it is a pay to play proposition. Anyone know?

The problem is that it has been so long since college that I am having a tough time relearning enough about linear systems analysis, state space representation, factoring of complex polynomials etc. to get the job done. Dang I have forgotten a lot!

The circuit in question is exemplified by the LP section of this Broskie rendering.

SY · 23rd July 2008, 11:14 PM

I don't have the original, but this is a pretty darn good explanation:

http://www.cimarrontechnology.com/pdf/sloa024a.pdf

mashaffer · 23rd July 2008, 11:42 PM

Thanks SY, I will spend some quality time with that one. Unfortunately it doesn't seem to deal with the single stage third order implementation. I assume the original paper deals with this as the circuit is so often attributed to them.

sidiy · 24th July 2008, 01:41 AM

Hi,
There's a online calculator here: http://www.beis.de/Elektronik/Filter/Act3PoleLP.html

You can also find a link to some of maths behind it.

23rd July 2008, 11:14 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I don't have the original, but this is a pretty darn good explanation: http://www.cimarrontechnology.com/pdf/sloa024a.pdf __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

23rd July 2008, 11:42 PM	#3
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	Thanks SY, I will spend some quality time with that one. Unfortunately it doesn't seem to deal with the single stage third order implementation. I assume the original paper deals with this as the circuit is so often attributed to them. __________________ mike - www.keepingsundayspecial.org

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24th July 2008, 01:41 AM	#4
sidiy diyAudio Member Join Date: Sep 2005 Location: Montreal	Hi, There's a online calculator here: http://www.beis.de/Elektronik/Filter/Act3PoleLP.html You can also find a link to some of maths behind it.

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