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It seems to me that the diagram shown here is less an active filter than an ac coupled inverting amplifier because the filter component is inactive. That is, it doesn't rely on the amplifier for its function in any way except for the virtual ground the amplifier provides. Its filtering function could be duplicated by a passive RC filter except for the buffering effect of the amplifier. The more common active filter would be in the form of a Sallen-Key filter (non-inverting) or a multiple feedback filter (inverting) in which the amplifier provides positive feedback to shape the filter's response and make it roll off more quickly into the stop-band. If I can figure out how to upload a diagram, I'll substitute a better one. Anoneditor 23:01, 11 July 2006 (UTC)
There is the beginnings of showing the "family tree" (taxonomy?) of filter types on the main filters page, but (quite rightly) it doesn't go into details of all the types of active filter available. I think something should be here; a diagram of some sort, but there are all sorts of ways to look at them, e.g. order of filter, number of amplifiers, high/low/band-pass etc, as well as an alphabetical list of names (yet textbooks are far from consistent in their use of names, and drilling down to see the circuits in such a list is a slow way of identifying a circuit you have in front of you). Also, there are details like mathematical treatment - zero/pole approaches - should that be the way to classify them (e.g. some books define second order in terms of the highest power of "s") - yet isn't that level of theory too far above the reading level this is pitched at? To go that way (which would be helpful to some readers) there would have to be lots of stuff added to wiki, like an easy explanation of all-pole for example.
Maitchy ( talk) 07:11, 4 August 2009 (UTC)
How about having a simple image for a low-pass and a band-pass active filters.-- Diraniyoussef ( talk) 06:08, 20 January 2021 (UTC)
A type of active filter that I've come across, is the leapfrog filter. It doesn't seem to be mentioned on Wikipedia yet. It is similar to the state variable filter, I think. It's probably worth both a mention on this page, and a separate article. -- HelgeStenstrom ( talk) 08:59, 26 October 2010 (UTC)
If the Twin T filter is a fully passive filter, why is it listed in this article which is about active filters?
ICE77 ( talk) 17:29, 11 May 2011 (UTC)
I guess the article should list the reasons why active filters are used and what are their advantages or disadvantages over passive filters.
ICE77 ( talk) 20:51, 13 December 2011 (UTC)
The reply to my initial comment by Wtshymanski is clearly not directly related to what I was trying to find out. In cases like this one, I suggest starting a new thread. Either way, active filters are not extinct. In fact, they are used in audio applications and a 3-way Linkwitz-Riley crossover is a very common example of active filters.
Dicklyon seems to point out the disadvantages of active filters by saying that they are more sensitive to component variation (I have read that in a book by Douglas Self on active filters where he was also saying that higher quality factors can be obtained). Dicklyon also says that the advantages of active filters are that inductors do not need to be used (so space and money can be saved). Before I start to take a look at the links Dicklyon provided, is there any other advantage/disadvantage for active filters?
ICE77 ( talk) 23:13, 28 December 2011 (UTC)
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It seems to me that the diagram shown here is less an active filter than an ac coupled inverting amplifier because the filter component is inactive. That is, it doesn't rely on the amplifier for its function in any way except for the virtual ground the amplifier provides. Its filtering function could be duplicated by a passive RC filter except for the buffering effect of the amplifier. The more common active filter would be in the form of a Sallen-Key filter (non-inverting) or a multiple feedback filter (inverting) in which the amplifier provides positive feedback to shape the filter's response and make it roll off more quickly into the stop-band. If I can figure out how to upload a diagram, I'll substitute a better one. Anoneditor 23:01, 11 July 2006 (UTC)
There is the beginnings of showing the "family tree" (taxonomy?) of filter types on the main filters page, but (quite rightly) it doesn't go into details of all the types of active filter available. I think something should be here; a diagram of some sort, but there are all sorts of ways to look at them, e.g. order of filter, number of amplifiers, high/low/band-pass etc, as well as an alphabetical list of names (yet textbooks are far from consistent in their use of names, and drilling down to see the circuits in such a list is a slow way of identifying a circuit you have in front of you). Also, there are details like mathematical treatment - zero/pole approaches - should that be the way to classify them (e.g. some books define second order in terms of the highest power of "s") - yet isn't that level of theory too far above the reading level this is pitched at? To go that way (which would be helpful to some readers) there would have to be lots of stuff added to wiki, like an easy explanation of all-pole for example.
Maitchy ( talk) 07:11, 4 August 2009 (UTC)
How about having a simple image for a low-pass and a band-pass active filters.-- Diraniyoussef ( talk) 06:08, 20 January 2021 (UTC)
A type of active filter that I've come across, is the leapfrog filter. It doesn't seem to be mentioned on Wikipedia yet. It is similar to the state variable filter, I think. It's probably worth both a mention on this page, and a separate article. -- HelgeStenstrom ( talk) 08:59, 26 October 2010 (UTC)
If the Twin T filter is a fully passive filter, why is it listed in this article which is about active filters?
ICE77 ( talk) 17:29, 11 May 2011 (UTC)
I guess the article should list the reasons why active filters are used and what are their advantages or disadvantages over passive filters.
ICE77 ( talk) 20:51, 13 December 2011 (UTC)
The reply to my initial comment by Wtshymanski is clearly not directly related to what I was trying to find out. In cases like this one, I suggest starting a new thread. Either way, active filters are not extinct. In fact, they are used in audio applications and a 3-way Linkwitz-Riley crossover is a very common example of active filters.
Dicklyon seems to point out the disadvantages of active filters by saying that they are more sensitive to component variation (I have read that in a book by Douglas Self on active filters where he was also saying that higher quality factors can be obtained). Dicklyon also says that the advantages of active filters are that inductors do not need to be used (so space and money can be saved). Before I start to take a look at the links Dicklyon provided, is there any other advantage/disadvantage for active filters?
ICE77 ( talk) 23:13, 28 December 2011 (UTC)
Hello fellow Wikipedians,
I have just modified one external link on Active filter. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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This message was posted before February 2018.
After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than
regular verification using the archive tool instructions below. Editors
have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the
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(last update: 5 June 2024).
Cheers.— InternetArchiveBot ( Report bug) 07:27, 26 June 2017 (UTC)