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Old 22nd June 2004, 10:30 PM   #1
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Default GC SuperSymmetry pt III

Of course a chip amp is very versatile. This version inverts
the input polarities and accomplishes the same thing.

Notice the nested loops, and the resistor in the center which
is the SS connection.

www.passlabs.com/np/GC-SS-3a.pdf

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Old 23rd June 2004, 02:08 AM   #2
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Well, National >does< call them 'smart transistors', and in
this context it helps to think of them that way. Using
the voltage rails to drive the output transistors still doesn't
look 'right' at first until I think of the chips as a transistor
with emitter and collector--with differential bases!

Then the pieces of the puzzle fall into place and I can start
to see the picture. I was going to object to the idea that
the chips themselves were plenty powerful, but with the
nested feedback that concept jumps ahead and looks much
more interesting!

This might be worth that headache after all.

Arigato, sensei; this slow student may be learning to think, however slowly.

Next question: does that 'transistor' actually behave something
like a discrete transistor? There may be surprises lurking within.
The "collector" and "emitter" might be very symmetrical in
behavior, unlike a discrete transistor (we hope so!), but are
they really linear?

I suspect this is a case where a CCS would be inappropriate.

This is all the time I have to puzzle over it; have to go fix supper!
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Old 23rd June 2004, 05:18 AM   #3
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Quote:
Originally posted by Damon Hill
does that 'transistor' actually behave something
like a discrete transistor? There may be surprises lurking within.
The "collector" and "emitter" might be very symmetrical in
behavior, unlike a discrete transistor (we hope so!), but are
they really linear?
With the local feedback around the chip it looks a lot like some
sort of idealized transistor, but you surmise correctly about
the potential for surprises.

The is in the details.
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Old 24th June 2004, 10:06 PM   #4
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Go.to.bed:

The 3a hardly looks SuperSymmetric.
I would try X-shape feedbacks from the outputs to the + nodes of the chips.
Euro2004 adds my lack of .
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Old 25th June 2004, 10:51 AM   #5
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Variazioni.Goldberg:

Here is the correction
Attached Images
File Type: jpg gc ss 3a_1.jpg (37.7 KB, 378 views)
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Old 25th June 2004, 11:13 AM   #6
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jh6you, that's much better. At least it looks way better
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Old 25th June 2004, 11:24 AM   #7
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Question Chipamps here?

I never thought Mr. Pass would ever use an op-amp.
Well... times they are a'changin' I guess...
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Old 25th June 2004, 11:35 AM   #8
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Default Xed already

Quote:
Originally posted by jh6you

The 3a hardly looks SuperSymmetric.
Hi,

in this case the SuSy is implemented already by the single

resistor between the opamps outputs.

Uli

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Old 25th June 2004, 01:40 PM   #9
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Uli.Buli:

What about this?
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File Type: jpg gc ss 3a_2.jpg (32.0 KB, 322 views)
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Old 25th June 2004, 01:57 PM   #10
uli is offline uli  Austria
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Wink don`t know

Hi,

I do not know yet, have to think it over

The magic resistor between the OPAs outputs feeds error

current into the output of the other OPA thus causing this amp

to feed reverse current into this resistor. This error current is

drawn from the supply. This in turn leads to creating this error

current out of phase at the output -> SuSy.

Your pic is indeed food for thought

Uli

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