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Old 10th July 2011, 02:40 PM   #1
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Default Nothing to see here

And you were expecting normal?
Attached Images
File Type: gif NothingToSeeHere.gif (27.2 KB, 615 views)
Attached Files
File Type: txt NothingToSeeHere.asc.txt (14.9 KB, 58 views)
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Old 10th July 2011, 05:01 PM   #2
jez is offline jez  United Kingdom
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Do you work for the Transistor Marketing Board by any chance
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Old 10th July 2011, 05:10 PM   #3
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Looks perfect for an SMD project - but what level of noise do you sim, relative to a 1V input say?
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Old 10th July 2011, 06:51 PM   #4
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Quote:
Originally Posted by jez View Post
Do you work for the Transistor Marketing Board by any chance
Yes of course, and 12R council too. Cheaper by the thousand!
All of three pennies or less at the local surplus store.

Consider 4 transistor arrays such as mmpq2907 and mmpq3906.
Especially where bonded device temps might be advantageous.
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Old 10th July 2011, 07:05 PM   #5
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Quote:
Originally Posted by Ian Finch View Post
Looks perfect for an SMD project - but what level of noise do you sim, relative to a 1V input say?
I provided the .asc file, just so you could tell me.

1V LTSpice (2VPP) input would be soft clipped by the Zeners.
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Old 10th July 2011, 08:22 PM   #6
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Quote:
Originally Posted by kenpeter View Post
Consider 4 transistor arrays such as mmpq2907 and mmpq3906.
Especially where bonded device temps might be advantageous.
Uh... I think I must have meant mmpq3904 (NPN) and mmpq3906 (PNP).
Dunno where "2907" came from?
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Old 10th July 2011, 08:31 PM   #7
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Nice one. I ran it through LTspice. As far as I can tell, it is all about the soft clipping. The input stage is certainly very interesting, and I'm still trying to take it all in.
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Old 11th July 2011, 04:26 AM   #8
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Nevermind soft clipping at +/-22V, and +/-6.5A,
nor a non-switching AB crossover. None of that
stuff even slightly important. The secret entirely
about rounding sharp corners off the schematic!

No-one else has figured this by now? As nature
abhors a vacuum, so too does LTSpice abhor a
sharp corner. Place an oil slick there, and watch
the electrons spin wildly out of control into the
grandstands.

I've added 22uF in series with R5, and 680R+68pF
across R8. Defining -3dB rolloffs at 5Hz and 96KHz.

Last edited by kenpeter; 11th July 2011 at 04:39 AM.
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Old 12th July 2011, 07:07 AM   #9
Elvee is offline Elvee  Belgium
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Intriguing circuit, especially the input stage.
But the performances do not seem to match the complexity however.

The input stage has a number of symetries, and by some aspects it reminds me of cross-quads, but stacked vertically.
Except there is a rather large ratio between the collector current of say Q3, Q19 and Q5, Q8 f.e.: this and the 470R coupling resistors ruin most of the Xquad effects.

What is this topology supposed to achieve, Ken? (Apart from the clipping control and Iq control, which are pretty obvious.)
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Old 12th July 2011, 07:40 AM   #10
dadod is offline dadod  Croatia
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Quote:
Originally Posted by kenpeter View Post
Yes of course, and 12R council too. Cheaper by the thousand!
All of three pennies or less at the local surplus store.

Consider 4 transistor arrays such as mmpq2907 and mmpq3906.
Especially where bonded device temps might be advantageous.
Because of 12R council you have 53MHz oscilation here.
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