Well, as I said, nothing comprehensive. A couple of allusions by Nelson to his non-switching patent which I was going to discuss here. A reference the the D. Self bias circuit which in my eyes is just an extraordinarily stable static bias generator, i.e. in its published form it does nothing to provide dynamic bias. The rest is all bits and pieces with passing reference taken to this or that design which is why I thought a dedicated thread might be justified.
Greetings,
Eric
Greetings,
Eric
That is an interesting Challenge!
I have, with pen and papper,
tried to find a satisfactory solution,
that never lets one transistor's Current go below a certain point,
while the other is conducting output current.
Of cource this is possible, but I have tried
to find a so easy and simple way as possible.
Not found it yet.
I'll tell you when I have.
Haven't dealt with that problem for a long time.
I have, with pen and papper,
tried to find a satisfactory solution,
that never lets one transistor's Current go below a certain point,
while the other is conducting output current.
Of cource this is possible, but I have tried
to find a so easy and simple way as possible.
Not found it yet.
I'll tell you when I have.
Haven't dealt with that problem for a long time.
Cross over noise is absolutly unacceptable by my standards.
I will post it later.
Crossover distortion is not just noise, but also linear distortion that sounds so disgusting if not reduced to acceptable scale.
Solution: Feedback Error Eorrection, Feedforward EC, and many other.
Currently I am using 30-70mA feedforward with crossing control, and Negative Feedback for main output stage (its still drift 40mA when cool 100mA when hot, I am going to fix it again sometime, I don't like thermal drift).
May be he forgot to post it.
Hi Eric,
Also have a look at:
Auto Bias part II
and http://www.diyaudio.com/forums/solid-state/145013-variable-operating-biass-output-8.html#post2233408
Hope it helps.
Cheers,
E.
Also have a look at:
Auto Bias part II
and http://www.diyaudio.com/forums/solid-state/145013-variable-operating-biass-output-8.html#post2233408
Hope it helps.
Cheers,
E.
Some in EW & WW :
Margan (non-passing branch becomes a CCS )
Jager (output using common emitters)
http://francis.audio2.pagesperso-orange.fr/C31_Jager.gif
Renardson (feed forward)
Audio Amplifier Circuit Design
Van de Gevel (common mode feedback loop)
Margan (non-passing branch becomes a CCS )
Jager (output using common emitters)
http://francis.audio2.pagesperso-orange.fr/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-orange.fr/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
http://www.diyaudio.com/forums/solid-state/92412-why-collector-drain-output-stages-so-rare-4.html
I have this found:
Perhaps one of the members knows an URL for download this article as PDF file or can post a scan of this article.
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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)
>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)
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?
http://home.tiscali.nl/data.odyssey/files/Jager/
do you know commercial amps uses this topology and that one mentioned by post #11?
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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?
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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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.
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.
[FONT=Arial, sans-serif]Francis Brooke's simulations of Jager's amp :
[/FONT]
[FONT=Arial, sans-serif]53 Weff/5.5ohm[/FONT]
[FONT=Arial, sans-serif]H2/H1=-81dB and H3/H1=-88dB for Vout=4Vc à 1kHz for a load of R=5.5ohm[/FONT]
[FONT=Arial, sans-serif]Vd out : 3mV at 27°C (Iq = 100mA) and 2mV at 75°C (Iq = 110mA)[/FONT]
[FONT=Arial, sans-serif]PSRR : 59dB[/FONT]
[FONT=Arial, sans-serif]Square wave 1kHz : overshoot 8% for a load of 8ohm//0.1µF and 4% for 8ohm//1µF[/FONT]
[FONT=Arial, sans-serif]Zout : 2,7 mOhm [/FONT][FONT=Arial, sans-serif]for a load of 5,5 Ohm[/FONT]
[FONT=Arial, sans-serif]Good thermal behaviour but low maximum slew-rate and output transistors need to be fast.
[/FONT]
[FONT=Arial, sans-serif]
[/FONT]
[/FONT]
[FONT=Arial, sans-serif]53 Weff/5.5ohm[/FONT]
[FONT=Arial, sans-serif]H2/H1=-81dB and H3/H1=-88dB for Vout=4Vc à 1kHz for a load of R=5.5ohm[/FONT]
[FONT=Arial, sans-serif]Vd out : 3mV at 27°C (Iq = 100mA) and 2mV at 75°C (Iq = 110mA)[/FONT]
[FONT=Arial, sans-serif]PSRR : 59dB[/FONT]
[FONT=Arial, sans-serif]Square wave 1kHz : overshoot 8% for a load of 8ohm//0.1µF and 4% for 8ohm//1µF[/FONT]
[FONT=Arial, sans-serif]Zout : 2,7 mOhm [/FONT][FONT=Arial, sans-serif]for a load of 5,5 Ohm[/FONT]
[FONT=Arial, sans-serif]Good thermal behaviour but low maximum slew-rate and output transistors need to be fast.
[/FONT]
[FONT=Arial, sans-serif]
[/FONT]
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
http://www.diyaudio.com/forums/solid-state/92412-why-collector-drain-output-stages-so-rare-5.html
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
http://www.diyaudio.com/forums/solid-state/92412-why-collector-drain-output-stages-so-rare-5.html
Do you know any types?
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