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Old 2nd November 2007, 08:27 PM   #61
dimitri is offline dimitri  United States
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Any news on the project?
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Old 30th November 2007, 07:53 PM   #62
marus is offline marus  Romania
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Where are the pictures and schematics from this thread ? I don't see any ... From the beginig there are no schematiscs ...
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Old 30th November 2007, 07:58 PM   #63
Tim__x is offline Tim__x  Canada
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This thread is three years old, sadly it seems Eva has removed the pictures from her website.
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Old 1st December 2007, 10:24 AM   #64
Eva is offline Eva  Spain
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The images were not deleted, they were just moved to a case sensitive host and the original files happen to have the name in upper case while I used lower case in my posts. I think that I have fixed all the file names. The same problem happens with the images that I posted in other old threads.

The breadboards of this project are still resting in one corner covered with a plastic bag to avoid dust. I may continue some day, but now I'm deeply involved into class D development, as lumanuaw cleverly predicted almost two years ago. Some of my current class D work may be seen in the class D forum.
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Old 1st December 2007, 08:04 PM   #65
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Default I will follow your class D project.


I am interested to learn and to construct to my own use.

regards,

Carlos
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Old 5th April 2010, 10:38 AM   #66
ontoaba is offline ontoaba  Indonesia
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Default Sorry it is long ago, just to say thanks.

Actually I'm searching for cheap amp project, but I've found this kind of input stage. It is new for me and I think I've got the point, a strong differential.
May I ask you your experience with this stage? Is there ever a problem caused by this input? Because it is very rare, might there some errr.
I have planning to use this kind in my follower amp, it need stronger differential than currently used.
Sorry this thread was long ago, but thanks for this post.


I'm stopped designing class-D but I'll just looking at yours.
Sadly this project ended here. I've enough experiencing myself with DMOS in power conversion and Amps, Floating Driver is the best way DMOS Amps for me.
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Old 5th April 2010, 02:14 PM   #67
ontoaba is offline ontoaba  Indonesia
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I'm realize some disadvantage in this differential, now.
Yes it has stronger gain, but it is not much better. Some transistor already with almost constant Vbe at certain current region.
Both input will interfere, and some more problem, like stability and performance in stressed condition.
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Old 5th April 2010, 03:44 PM   #68
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MOSFET's are limited by the package they are in for power dissipation.
Some specs seem a bit optimistic to me especially the IRFP260.

I usually use IRFP240's (1-50) in my designs as they are cheap and not optimistic with power rating.

I believe an amplifier needs cross conduction to get rid of crossover distortion.
Simulations can be used as general pointers but are rarely exact.
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Old 5th April 2010, 04:32 PM   #69
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by onto aban View Post
I'm realize some disadvantage in this differential, now.
Yes it has stronger gain, but it is not much better. Some transistor already with almost constant Vbe at certain current region.
Both input will interfere, and some more problem, like stability and performance in stressed condition.
I think you dismiss this circuit a bit too quickly: it is very smart and clever indeed (what else would you expect from Eva?..).
It looks like a variation on the Xquad, but without some of its problems.
The accuracy and linearity, compared to a plain differential, are outstanding: practically one order of magnitude improvement.
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Old 6th April 2010, 12:17 AM   #70
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Originally Posted by Eva View Post
That's pseudo-class-A stuff. It keeps the ouput devices always biased to an adjustable current level (R79 and R80) and there is another "AC cross-conduction" adjustment (R78). That reduces gate-charging spikes (the ones in Ic(Q17) and Ic(Q18)) to an absolute minimum. These waveforms also show the extreme non-linearity that MOSFET devices show in class-B at high frequencies, even in the harmless PSpice models with linear capacitances.

In PSpice it looks beautiful, as always...
I have a much simpler diode crossed output stage that does exactly this.
But an entirely different method, and drastically lower parts count. Search
my recent posts... Granted, I havn't yet tried grafting your input stage
with my output. That combo might be a winner... My methods are kinda
screwy: I do let Schottky devices sometimes turn off, but only Schottky.

You demand the right set of always-on AB curves for sure. I agree with
need for active pull up and down when it comes to driving MOSFET gate
capacitance with any symmetry, you got that right too. Just throwing a
few too many parts at an analog computing and driving problem that can
be solved an easier way.

Last edited by kenpeter; 6th April 2010 at 12:24 AM.
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