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Old 19th April 2005, 07:15 AM   #21
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Old 18th April 2007, 02:52 PM   #22
Ecess is offline Ecess  France
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Default Susytron

Hello, Circlomanen.

I was very interested in your “cyclotron” work. The two floating power supplies remind me the development of Parallel Push Pull (P3 power set) with tubes in the 50’s.
You said on the forum that it did not work. Did you carry advanced tests since ?
I wonder whether the Susy folded cascode can work properly under fairly variable supply rails ?
In your drawing of 2005, the unique input Mosfet gain stage imposes a polarisation of the gate that moves with the output. It questions me.
As per the schematic below, I would rather use a unique negative feed back by the sources and a third power supply for the gain stage.

In reference to your ideas and Nelson Pass work, I call it Susytron, while in fact it is not that much super symmetry since sources of the input MosFet’s are now referenced to ground or zero of the third power supply and middle point of the load, as well.
I have included cascoded power stages in order to draw convenient power. Compared to the US patent of Nelson on the cascoding principle, here the cascoding transistor carry the full bias current of the 2SK1058, because I got rid off the Current Power Supply across them. Three power supplies is already enough ! The cascoding transistor dissipate about 26 watts each…

The Mosfet’s I propose (2SK214, 2SJ77, 2SK1058) are well known audio Mosfets. They are ESD protected, negative temperature coefficient from Vgsth upward and exhibit a Vgsth very close to zero which simplifies implementation and increases dynamics. But they are fairly low current devices and fairly expensive.

Your comments are welcome.
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Old 18th April 2007, 05:42 PM   #23
DIGORA is offline DIGORA  Belgium
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le principe n'est pas d'utiliser les même transistor pour le signal et la cascode ?

Mais je ne vois pas de susy ..
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Old 19th April 2007, 10:06 AM   #24
Ecess is offline Ecess  France
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Hello DIGORA.

Cascode device type.
May be some one else should answer your question.
If nobody does, I will give you my understanding of the Cascode concept in a later post and why I think one should select appropriate devices for two different modes : the cascoded mode and the cascoding mode. The concept in itself is very well explained in the Pass US Patent N°5343166.

Susy or not Susy ?
You are right, this is not a Susy design.
I apologize for the misuse of the concept, but I did mention in my post that it was not a Susy thing.

You will find below a new schematic which bring back the prospective work of Mr Circlomanen into the “Susy world” by means of a CCS in the sources path of the input Mosfet’s. Now the third power supply needs to be a + and – V.
At the same time one would be happy to get rid off the input capacitor and the questionable biasing of these input Mosfet’s.

Speaking of Ciclotron, I read that Mr Grey Rollins has given us a post on using power J Fet in such a concept. Sorry Grey, to discover that on the late.
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Old 19th April 2007, 07:07 PM   #25
Stefano is offline Stefano  Italy
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"Speaking of Ciclotron, I read that Mr Grey Rollins has given us a post on using power J Fet in such a concept. Sorry Grey, to discover that on the late."

Where did you find it?
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Old 20th April 2007, 12:19 PM   #26
Ecess is offline Ecess  France
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Well Stefano,
I spent a fair amount of time looking at every thing that has been discussed on the Pass Labs forum around X serie and Aleph. I have seen so many that I would not be able to say precisely where.

But I kept the Pdf of the schematic he discussed. Do you want it ?
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Old 20th April 2007, 03:20 PM   #27
Stefano is offline Stefano  Italy
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I wuold be very pleased if you wuold send it to me, my mail is tuamamma@gmail.com

Thank you very much!!!
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