Talk:Electronic filter topology

Proposed merge
I think the separate articles should be kept separate. They are not in danger of deletion, and they will only grow larger, not smaller. Rather than combine now and then separate out again later when they grow large, lets leave them as separate article with this page as a convenient jumping off point. No need to wonder whether this page has the article, or whether its been separated out. PAR (talk) 05:10, 29 November 2007 (UTC)


 * Well, the redirect for the individual topics would take you directly to their section in the main article, so users looking for a specific topic wouldn't be totally lost. Being part of this article wouldn't prevent those topics from being expanded, and we could always break them out later if they become too long.  (For another thing, these haven't been significantly expanded since they were written a year ago.)   I think these very much are at risk of being deleted, as they're currently stubs and really don't assert notability, and I think combined they would make this article better than the sum of its parts. Torc2 (talk) 07:28, 29 November 2007 (UTC)


 * I agree with Torc2. I think putting the little stubs together now will make a better article. Certainly we'll split this article back up again if it gets too long -- but in my opinion, pre-splitting ahead of time because we *think* small stubs will grow into a small article is generally mis-guided. I've found it is usually better to let a large article accumulate information about a sub topic, until it is so long that we can split off one or more a small articles full-fledged."big buckets first". --75.19.73.101 (talk) 07:38, 16 December 2007 (UTC)


 * I disagree with Torc2 and the merge for two reasons:


 * it would make the Electronic filter topology article too large (even with the amount of material there now) and so difficult to read,
 * it doesn't make the organisation any neater - for example, is there any reason they should go here rather than in Active Filters?
 * It would, however, be reasonable to insert brief discussion of the broad division of active filter topologies, like those using feedback to the inverting input and those in the negative feedback.

Maitchy (talk) 23:37, 18 January 2009 (UTC)

I'm against this. I am planning on writing a lengthy article on Zobel networks. It would not be sensible to merge this article with the proposed merge, but a filter topology article is a good jumping off point for it. I may well follow this with an article on constant k and m-derived filters. These are variations of the Cauer topology and may result in some expansion of that article as well. However, the three "op-amp" topologies, Sallen-Key, Multiple Feedback and State Variable I agree could be merged, at least as they stand now. The Cauer topology is a different animal, I feel, and should be left separate, as should the topologies page.  Sp in ni ng  Spark  16:37, 2 March 2008 (UTC)


 * The article can be spun back off when it becomes long enough.  &mdash;Torc.  ( Talk. ) 08:17, 3 March 2008 (UTC)


 * Ok, I have finished doing what I needed to do to this article. I withdraw my objection, go ahead and merge if you think it is still necessary.  By the way, most of the stuff in Cauer topology (electronics) is about driving point impedance and belongs in Network synthesis as it has naff all to do with topology.  Sp in ni  ng  Spark  20:31, 30 June 2008 (UTC)


 * I have merged this article (it has been templated for a long time and no one else looked like they were going to do anything), but not into the place the merge template was pointing to. The material is now at network synthesis filters which is what the material really relates to.  The redirect however, is pointing to the relevant section of electronic filter topology.  Sp in ni  ng  Spark  15:23, 28 September 2008 (UTC)

Natural frequency
The reason I think your natural frequency equation is wrong is because R3 control the Q of the second order system so for all R's and C's equal (except for R3 which should be sized as Q*R), your natural frequency should be 1/RC not 1/(sqrt(Q)*RC). http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00491051 and http://cng.ateneo.edu/cng/wyu/works/papers/tow-thomas.pdf should confirm the changes I made.
 * You're right, my apologies. I have self-reverted.  Sp in ni  ng  Spark  07:01, 30 April 2010 (UTC)

Ladder topology inventor
The article claims that "Ladder topology, often called Cauer topology after Wilhelm Cauer (inventor of the elliptic filter), was in fact first used by George Campbell (inventor of the constant k filter). Campbell published in 1922 but had clearly been using the topology for some time before this."

If that is the case and Campbell used the ladder topology before 1922, why is the topology called Cauer and not Campbell?

ICE77 (talk) 16:32, 6 August 2015 (UTC)


 * There is no "if" about it. Campbell unarguably used the ladder topology, as can be verified by numerous sources.  There is also pretty much no doubt that he was first, since his 1922 filter was the first non-trivial electric filter in any topology.  It's not as if Campbell did not use the term ladder in his original paper; he did, repeatedly.
 * There is probably no citable answer to your question, there are numerous similar examples in science (why is the code called Morse when it was invented by Vail? Why is the bridge called Wheatstone when it was invented by Christie?). Often a thing comes to wider attention through someone of greater standing than the original inventor and gets their name instead.  My guess is that we only started talking about the realisation of a given transfer function in a given topology with Cauer (although Cauer's first topology involved lots of mutual inductances - but "Cauer's bird's nest" has been quietly forgotten about and his name has been put on the rather more practical ladder instead.) SpinningSpark 17:58, 6 August 2015 (UTC)

Tow-Thomas circuit
Is the Tow-Thomas circuit an example of single-amplifier biquad or two-integrator-loop circuit?

ICE77 (talk) 21:48, 28 October 2015 (UTC)

Akerberg-Mossberg schematic
The bottom right op-amp of the A-M schematic (the op-amp which provides the low-pass output) should have its INVERTING input grounded --- the opposite of most common uses. On the Web, pretty much only the University of Oregon duplicates this error. Note how the op-amp above inverts the signal, providing the necessary negative feedback. 73.207.126.214 (talk) 20:23, 27 March 2023 (UTC)