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Old 20th November 2011, 09:15 PM   #391
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Default Device

Edmond,
What about this device?
Lateral Mosfet
VDS : 200V
Is there a drawback in this component? Besides price I suppose and probably sourcing?
Cheers,
Olivier
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Old 20th November 2011, 09:22 PM   #392
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Quote:
Originally Posted by Olivier73 View Post
Edmond,
What about this device?
Lateral Mosfet
VDS : 200V
Is there a drawback in this component? Besides price I suppose and probably sourcing?
Cheers,
Olivier
Looks nice !
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Een volk dat voor tirannen zwicht, zal meer dan lijf en
goed verliezen dan dooft het licht…(H.M. van Randwijk)
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Old 20th November 2011, 09:39 PM   #393
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Hi again,

They are available at RS components belgium for 11.54€/pc (in stock). The 160V version.

I also like this one :
ALF16N20W for 10.86€ sadly the P channel is unavailable.
ALF08P20W for 6.59€
ALF08N20W for 6.59€

There is no rush in answering any questions. I respect all the time want to spend.

I will simulate the miller loop according to the components on the actual pcb and will come back to you with results. I will try again with my own circuit and if the result is still strange I will adapt your schematic file to the actual components. Maybe I'll do the latter first as it might be faster :-)

Cheers,

Olivier
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Old 21st November 2011, 05:11 PM   #394
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Default Class-I

Quote:
Originally Posted by Olivier73 View Post
Edmond,
What about this device?
Lateral Mosfet
VDS : 200V
Is there a drawback in this component? Besides price I suppose and probably sourcing?
Cheers,
Olivier
Sorry, NOT that nice because of a common source connection. So you cannot insert source series resistors.

Regarding the other laterals, I would wait to purchase them, as it not impossible that the specific advantages of verticals outweigh the virtues of laterals.
The point is that someone kindly provided me a glimps into Kendall Castor-Perry's Class-I output stage, that is, a very basic sketch. So I don't know any details, but you can find it here: Linear Audio | your tech audio resource

In the meantime I figured out how his circuit might work and I must say (if my implementation is correct) that Kendall is really a genius. His circuit works even better than my autobias-II thingy: more tolerant to component mismatches and Iq is less temperature dependent (0.1%/K versus 0.3%/K). Brilliant! Chapeau!

Below you see a relative low power version with only one pair of vertical MOSFETs. The performance with laterals was less favorable, due to the extreme low Vgth and (probably) lower transconductance.

Notice that the use of separate push-pull drivers is an absolute necessity, as you can't use a single PNP-NPN EF stage with the ubiquitous speed-up cap between the emitters. Such a cap destroys the whole concept. Deleting the cap isn't an option either, as this will provoke cross-conduction.

Also notice the frequency compensation: C3, R8, C4 & R9. I don't know if Kendall did it the same way, but I think this is the only correct method (i.e. feed-through compensation)

Please have a look at it and/or run a sim. THD20 is really low: ~67ppm.
(but first the Miller loop, of course )

Cheers,
E.
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File Type: png Class-I.png (34.2 KB, 300 views)
Attached Files
File Type: txt OPS4.CIR.TXT (51.5 KB, 47 views)
__________________
Een volk dat voor tirannen zwicht, zal meer dan lijf en
goed verliezen dan dooft het licht…(H.M. van Randwijk)

Last edited by Edmond Stuart; 21st November 2011 at 05:17 PM.
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Old 23rd November 2011, 04:36 PM   #395
dadod is offline dadod  Croatia
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Very interesting. Can you give some simulation numbers? It's a pity I can not use your file for LTspice.
dado
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Old 23rd November 2011, 04:59 PM   #396
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Default Class-I

Hi Damir,

Maybe you have overlooked it, but the most important key figures are mentioned in the schematic (red text). I a couple of days I hope to give some more information in a separate thread.

To all,
Does anyone have the original article from Kendall? I don't have a copy. Much obliged if someone would send me a (scanned ) copy.

Cheers,
E.
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goed verliezen dan dooft het licht…(H.M. van Randwijk)
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Old 23rd November 2011, 05:38 PM   #397
dadod is offline dadod  Croatia
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Hi Edmond,
Yes I have seen those figures. I am waiting to see more about this output stage. If I understood correctly this uniti-gain stage.
Damir
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Old 23rd November 2011, 08:04 PM   #398
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Hi Edmond,
I still cannot figure out why my circuit does not show a correct millerloop response!?
I will continue to check.
However I stepped to your circuit for comparison.
I have a question anyway : the ML response around 200KHz shows a phase margin much lower than 90°. More like 40° ... is that a problem? What does affect the Phase in this circuit? Can it be optimized?
Cheers
Olivier
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Old 23rd November 2011, 08:06 PM   #399
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Well it's not that bad in your last post ... it's less than 90 but not so much anyway... sorry
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Old 23rd November 2011, 08:48 PM   #400
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Unhappy Millerloop Response

Edmond,
I don't get it !?
Could you run my MC9 file to see if you get a good result or if you get the same bad result I do (see AC analyses joined)?
Thanks
Olivier
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File Type: txt Millertest.cir.txt (69.0 KB, 25 views)
File Type: pdf AC Analysis.pdf (16.4 KB, 52 views)
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