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Old 3rd May 2011, 03:56 PM   #11
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Hi Eric,

Also have a look at:
Auto Bias part II
and Variable operating biass output ?
Hope it helps.

Cheers,
E.
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Old 3rd May 2011, 05:35 PM   #12
forr is offline forr  France
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Some in EW & WW :

Margan (non-passing branch becomes a CCS )

Jager (output using common emitters)
http://francis.audio2.pagesperso-ora.../C31_Jager.gif

Renardson (feed forward)
Audio Amplifier Circuit Design

Van de Gevel (common mode feedback loop)
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Old 4th May 2011, 12:07 AM   #13
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Quote:
Originally Posted by forr View Post
Some in EW & WW :

Margan (non-passing branch becomes a CCS )
Jager (output using common emitters)
http://francis.audio2.pagesperso-ora.../C31_Jager.gif
Renardson (feed forward)
Audio Amplifier Circuit Design
Van de Gevel (common mode feedback loop)
Jager (output using common emitters)
http://francis.audio2.pagesperso-ora.../C31_Jager.gif
Was that topology from the article
"A new Class AB design"
from the authors Wim de Jager,
van Tuy & van der Ven (University of Twente)
Electronics World, December 1999, Page 982 ??
If yes, I am looking for this article because I don't find this magazine, that I bought 1999 at my local railway station book-shop (maybe misplaced or borrowed and not get back).

Additional questions:
1) Are this topology to find in commercial audio amplifiers?
2) What is the colloquial term of this Class AB topology?

By post #32 about
Why collector/drain output stages are so rare???
I have this found:
Quote:
Originally Posted by forr View Post
More information on the above amp :
Wim de Jager, Erik van der Ven, Ed van Tuyl
ELECTRONICS WORLD December 1999 pp. 982 – 987
"This class-AB common-emitter power amplifier incorporates a new current-mode class-AB driver circuit to obtain good thermal stability of the quiescent current in the output stage. It also guarantees non-zero currents in the output transistor that is conducting the residual current, avoiding HF switching distortion. Maximum output voltage is near to the rail to rail limit. Saturation of the power transistors is avoided, resulting in fast recovering from clipping. The circuit has an excellent stability due to a phase margin of 85 ° with a b 1/34"
Perhaps one of the members knows an URL for download this article as PDF file or can post a scan of this article.

Last edited by tiefbassuebertr; 4th May 2011 at 12:20 AM.
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Old 4th May 2011, 06:07 AM   #14
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Default de Jager et al.

>Perhaps one of the members knows an URL for download this article as PDF file or can post a scan of this article.

Please look here:
Index of /data.odyssey/files/Jager (6 pdf's)
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Old 4th May 2011, 06:45 AM   #15
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Thank you very much for this URL:
http://home.tiscali.nl/data.odyssey/files/Jager/
do you know commercial amps uses this topology and that one mentioned by post #11?

Last edited by tiefbassuebertr; 4th May 2011 at 06:49 AM.
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Old 4th May 2011, 06:49 AM   #16
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Thank you for posting this article reference Edmond, very interesting.
One is tempted to think that Jager's scheme works very well at reducing crossover distortion.
So, as I don't see wide use or even adaptation, what is the catch - or perhaps difficulty that deters us?

Would anyone familiar with this design care to comment?
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Last edited by Ian Finch; 4th May 2011 at 06:51 AM.
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Old 4th May 2011, 07:22 AM   #17
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Quote:
Originally Posted by tiefbassuebertr View Post
Thank you very much for this URL:
Index of /data.odyssey/files/Jager
You're welcome.

Quote:
do you know commercial amps uses this topology and that one mentioned by post #11?
No, I don't know.

Cheers,
E.
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Old 4th May 2011, 07:41 AM   #18
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Quote:
Originally Posted by Ian Finch View Post
Thank you for posting this article reference Edmond, very interesting.

You're welcome.

Quote:
One is tempted to think that Jager's scheme works very well at reducing crossover distortion.
So, as I don't see wide use or even adaptation, what is the catch - or perhaps difficulty that deters us?
..........
Years ago, I've simulated this amp and as far as I can remember, results were not that spectacular. At the high end of the audio spectrum distortion AND cross-conduction rises sharply.

I'm not aware of any commercial power amp using this topology, but according to the references, it seems that this technique has found application in IC based op-amps.

Cheers,
E.
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Old 4th May 2011, 09:20 AM   #19
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Francis Brooke's simulations of Jager's amp :

53 Weff/5.5ohm

H2/H1=-81dB and H3/H1=-88dB for Vout=4Vc ŕ 1kHz for a load of R=5.5ohm

Vd out : 3mV at 27°C (Iq = 100mA) and 2mV at 75°C (Iq = 110mA)
PSRR : 59dB

Square wave 1kHz : overshoot 8% for a load of 8ohm//0.1µF and 4% for 8ohm//1µF

Zout : 2,7 mOhm for a load of 5,5 Ohm

Good thermal behaviour but low maximum slew-rate and output transistors need to be fast.


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Old 4th May 2011, 11:18 AM   #20
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Quote:
Originally Posted by Edmond Stuart View Post
You're welcome.
Years ago, I've simulated this amp and as far as I can remember, results were not that spectacular. At the high end of the audio spectrum distortion AND cross-conduction rises sharply.Cheers, E.
The disadvantage of BjT power devices in that topology is the smaller value of ft. Therefore the differences between class AB and pure class-A in the upper range are even greater than in normal power follower circuit.
by post #42 (URL's about Abacus and LEF) about
Why collector/drain output stages are so rare???
there are other advantages mentioned, but this advantages more useful in the low frequency aera (causes impedances with inductive character and thus phase shifting effects between voltage and current).
For me is the conclusion, that this topology is to prefer for "high power" subwoofer power amps with low efficiency speakers like JL audio's "13W7AE", where the desire of a high quiescent current stability must be present and no unwanted audible effects occur through phase shifts arround the resonance frequency from the drived bass loudspeaker system (by use of power follower output stages often a problem without impedance compensation network).
What about Linn's solution, realized by the model "Klout" ? - have a look to the attachement by post #42 about
Why collector/drain output stages are so rare???
Quote:
Originally Posted by Edmond Stuart View Post
I'm not aware of any commercial power amp using this topology, but according to the references, it seems that this technique has found application in IC based op-amps.
Do you know any types?

Last edited by tiefbassuebertr; 4th May 2011 at 11:35 AM.
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