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Old 9th December 2003, 03:20 AM   #11
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I think that the X-feedback cancells the signal distortion so much as controlled. And, the asymmetric cancellation of common mode signal is added to the total offset output voltage. I try to solve my problem from this point. Probably, I'm very wrong.
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Old 9th December 2003, 11:03 AM   #12
grataku is offline grataku  United States
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?
SuSy is just a buzzword
Common mode cancellation comes from the fact that the amp is differential, and has nothing to do with Susy.
You can either stop there and have nested differentials (BLS+ SOZ) or add feedback to connect the two stages. There are not many ways to achieve negative feedback with nested differentials.
When applicable, the idea is clever and it can be argued that the whole is more than the sum of the parts.

Without pulling Nelson's papers out, I don't recall seeing improved measurements for the SySy circuit. I can remember a lot of peanuts and chocolate that usually irritate my intestine.
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Old 11th December 2003, 07:08 PM   #13
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Hi Hugo,

I got it

Picture shows a 10kHz sine from a not so good Siemens function generator.

Marker is on 10kHz and cursor on 20kHz. 2nd harmonic is -55,7dB, there is a lot of other dirt like strong third harmonic and very strong 7th harmonic and even disharmonic crap.

Another better sine generator shows only 2nd and very little higher harmonics.

I can see down to -75dB very clear frozen curves without noisfloor by averaging up to 500 or more measurements and storing them.

Averaged & stored curves may be subracted from or added to each other

That means I can test all my madness circuits and see what's up


Greetings, Bernhard
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File Type: jpg sinussmall.jpg (98.3 KB, 258 views)
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Old 11th December 2003, 07:18 PM   #14
Netlist is offline Netlist  Belgium
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This must be a picture from the harmonics of a Madness circuit taken with your new toy.
Please elaborate a bit. How did you measure what?

/Hugo
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Old 11th December 2003, 07:22 PM   #15
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Weak signal from Explorer.....somewhere beyond solar system...
elaborate. SVP

rich
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Old 11th December 2003, 07:26 PM   #16
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Talking I'm in love with a machine

see edited post
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Old 11th December 2003, 07:28 PM   #17
grataku is offline grataku  United States
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It's more like: "I got a big spectrum analyzer but I don't know how to use it"...
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Old 11th December 2003, 07:34 PM   #18
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Quote:
Originally posted by grataku
It's more like: "I got a big spectrum analyzer but I don't know how to use it"...
I'm sure your's is bigger than mine

Don't worry...

Also the sine generator curve can be subtracted from the amp (+generator) curve, so the pure amp distortion is left.

Before doing serious things I have to play a little.
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Old 11th December 2003, 07:39 PM   #19
Netlist is offline Netlist  Belgium
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I also want a toy like that....

/Hugo
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Old 11th December 2003, 07:48 PM   #20
eLarson is offline eLarson  United States
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Default Super Symmetry as I understand it

The thing about SuperSymmetry is that it uses feedback around each half to make each half look more alike.

As far as I can see, it really works the same way as a regular differential circuit... it's just that we now have two halves matched better than normal, thanks to the feedback applied to each side.

edit: I believe it is supposed to 10x better than just regular differential. (factor of 100 cancellation vs. factor of 10.) I, too, am going by memory... ('watakashi-no kyoku-ga tashika naraba...')

eL
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