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Old 13th September 2004, 05:38 PM   #1
AndrewT is offline AndrewT  Scotland
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Default nested feedback loops

Dr. Cherry wrote a very techy article about nested fedback loops about two decades ago. I t has been reprinted in a few resources since, but I cannot access a copy.
Can any one out there point me to a resource from where I can download the article. It appeared in ETI and also as an AES ? paper.
Have you seen any alternative design info for NFL?
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Old 13th September 2004, 07:44 PM   #2
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NFL's have been around a long time - they had been thought
of 30 years ago that I know, and they quite simple to design
and implement. They work just like you think they would.
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Old 13th September 2004, 08:29 PM   #3
mikeks is offline mikeks  United Kingdom
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Default See...

..patent # 4243943 here:

www.uspto.gov


...also...conduct search here:

http://www.aes.org/journal/search.cfm

...papers may be purchased online...
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Old 13th September 2004, 08:31 PM   #4
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Default Re: nested feedback loops

Quote:
Originally posted by AndrewT
Dr. Cherry wrote a very techy article about nested fedback loops about two decades ago. I t has been reprinted in a few resources since, but I cannot access a copy.
Can any one out there point me to a resource from where I can download the article. It appeared in ETI and also as an AES ? paper.
Have you seen any alternative design info for NFL?

You can do a search on the www.aes.org site and purchase the paper online.

Jan Didden

Edit: It appears there is no AES paper on this. Hmm.

Edit2: yes there is:

Nested Differentiating Feedback Loops in Simple Audio Amplifiers
Volume 30 Number 5 pp. 295-305; May 1982
Many audio power amplifiers consist in essence of a long-tailed-pair first stage, a lag-compensated common-emitter stage with its emitter on a supply rail, a complementary-emitter-follower output stage, and overall negative feedback. Two nested differentiating feedback loops can be added to this basic topology, to achieve between one and two orders of magnitude reduction in distortion, at little increase in component cost. Six extra components are essential; two small-signal transistors, one resistor, and two capacitors. Further small components such as zener diodes and bypass capacitors may be required, depending on the details of the supply rails the amplifier.
Author: Cherry, Edward M.
E-lib Location: (CD aes4) /jrnl7888/1982/7852.pdf
downloadable electronic version PDF (1.1 MB) $5.00 AES Member | $10.00 Non-Member
hard copy $5.00 AES Member | $10.00 Non-Member
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Old 13th September 2004, 08:42 PM   #5
SY is offline SY  United States
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Quote:
Originally posted by Nelson Pass
NFL's have been around a long time - they had been thought
of 30 years ago that I know, and they quite simple to design
and implement. They work just like you think they would.
Longer even than that- Norman Crowhurst wrote about them in "Understanding HiFi Circuits" nearly 50 years ago (using hollow state devices), and it wasn't even new then.
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Old 13th September 2004, 11:45 PM   #6
AndrewT is offline AndrewT  Scotland
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Thanks all, I have some reading ahead of me. I hope Nelson is right & it all easily falls into place. Just not too many poles & zeros, I'm still struggling with the concept. regards Andrew T.
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