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 tiefbassuebertr 25th July 2009 10:13 AM

The most linear stage for large voltage swings - Lender's Circuit

The most linear stage for large voltage swings - Lender's Circuit

In my (already older) book from the magazine "Audio Amateur", title "Power Amp Projects" I have found the project from ERNO BORBELY "The 60W MOSFET POWER AMPLIFIER" On page 76 (column 2), I read - quotation -

================================================== ===============
The most linear stage for large voltage swings is the grounded base or common base amplifier. Unfortunately interfacing his stage with others is not easy because of biasing problems.
Lender (ref2) presents the most elegant solution to this problem. I have come across. His circuit has a differential input stage and a current mirror transfers the bal. output back to the single-ended output.
================================================== ================

so as an ref advice (ref 2) to very interest Motorola article from Mr. R. Lender
"Power Amplifier with darlingon output stage"
Motorola Inc., Geneva, Switzerland,
7.9.1974 internal report (July 9. or Sep. 7 - I don't know)

Who knows, where I can download this original article from Motorola ?
Also of interest for me are books and additional articles of Mr. R. Lender

This voltage gain stage topology you can find in several designs, e. g.
http://www.davidsaudio.com/assets/im...pzilla_sch.jpg (ampzilla)
or JBL stage power amplifier 6290
http://www.jblpro.com/catalog/genera...CatID=20&Run=1
and many other
This topology is a transitional form between folded cascode version (one stage voltage gain amp) and normal version (two gain stage voltage amp). I think, in the orig. article there are to read more about the calculation basics because it was written for development departments

http://www.tubecad.com/march2001/page25.html (I think, Linder is faulty name and Lender the right one)

 AndrewT 25th July 2009 10:26 AM

there are 18 other "Lender" results in the search function.
Here is one example:
http://www.diyaudio.com/forums/showt...726#post410726

 jan.didden 25th July 2009 03:37 PM

Re: The most linear stage for large voltage swings - Lender's Circuit

Quote:

Have you asked Erno? He may have a copy and/or willing to scan.

jd

 Bigun 25th July 2009 07:08 PM

This is indeed an approach with potential. I also came across the tube.cad article [http://www.diyaudio.com/forums/showt...44#post1847644] but I found it does suffer from producing imbalance in the LTP when not used as part of a symmetrical design such as Roender's folded cascode. You end up using a lot more parts than the simple Self single ended VAS.

 KSTR 25th July 2009 09:27 PM

Pavel (PMA) is using it, too, in the DisPre II. Albeit unbuffered and complementary.

- Klaus

 Bigun 25th July 2009 10:43 PM

This looks a little different than common base, more like a differential with input into the base and into the emitter ?

http://www.tpub.com/content/neets/14...s/14180_92.htm

 mlloyd1 26th July 2009 02:14 PM

just to throw it out there - there has been some discussion on "pseudo" folded cascode in a few places over the years. here's a couple of places i know about:
number 1 and number 2

warning: number 2 wandered off-topic quite a bit, as is usual around here.

mlloyd1

 tiefbassuebertr 31st July 2009 02:28 PM

Re: Re: The most linear stage for large voltage swings - Lender's Circuit

Thank you very much for the additional circuit advices with Lender's topology.

Quote:
 Originally posted by janneman Have you asked Erno? He may have a copy and/or willing to scan. jd
yes, already some years ago. Unfortunately he don't have the orig article

"Power Amplifier with darlingon output stage"
Motorola Inc., Geneva, Switzerland, 7.9.1974.

This article only the old, former Motorola employees can look out. Since then the field of power devices transits in the company "ON SEMI", it can also be that this article now by ON-SEMI is archived. This article was only available for large customers and otherwise in those days for internal use only. in any one days by this forum come up this article - so I hope.

 Lumba Ogir 2nd August 2009 02:47 AM

tiefbassuebertr,
Quote:
 The most linear stage for large voltage swings is the grounded base or common base amplifier.
Right.
Quote:
 Lender (ref2) presents the most elegant solution to this problem. I have come across.
It`s a mildly flattering solution resulting in something else.

 Bonsai 2nd August 2009 06:15 AM

for large voltage swings and great linearity, you might want to try Hawksfords VAS stage. I hav e not built it, but in sims its about 20 times better than a standard cascode on distortion.

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