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Old 21st June 2013, 07:29 PM   #1041
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Originally Posted by michaelkiwanuka View Post
I am not sure I comprehend; are you refering to your AD797?
There are others. Solomon jumps right to the answer. You can present the same op-amp as two cascaded voltage gain stages and show unconditional instability, then introduce the pole spliting effect of Ccomp. It is then possible to work in the right plane zero effects in the second stage. I would hope the goal is for folks to learn more than the "right" name for things.

As has been demonstrated a single folded cascode stage can, with enough bootstrapping, have DC gain of >5*10^6 and the same gm-C AC characteristics with Ccomp to ground.

Had to laugh, Solomon shows the 10.7kHz full power BW on the 741.
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Old 21st June 2013, 08:24 PM   #1042
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Had to laugh, Solomon shows the 10.7kHz full power BW on the 741.
Surely you jest!

LM301 was a favourite of mine in Jurassic days cos it was easy to disable the i/p stage to incorporate a nice LN BJT instead. All dis BS got swept into the Don't Recycle Bin once the TDA1034 (original name for NE5534) came out from Mullard.
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Old 21st June 2013, 08:36 PM   #1043
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TDA1034 came out from Mullard or was it Philips?
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Old 21st June 2013, 08:41 PM   #1044
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Originally Posted by scott wurcer View Post
I would hope the goal is for folks to learn more than the "right" name for things.
I think knowing the right name for things is an excellent starting point to knowing how they really work.

Quote:
Originally Posted by scott wurcer View Post
As has been demonstrated a single folded cascode stage can, with enough bootstrapping, have DC gain of >5*10^6 and the same gm-C AC characteristics with Ccomp to ground.
The only snag is shunt compensation to ground increases the non-linearity of the stage it compensates.

Be that as it may, it would be fascinating if you would produce a discrete amplifier for diyaudio based on your AD797.
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Old 21st June 2013, 09:03 PM   #1045
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Originally Posted by michaelkiwanuka View Post

Be that as it may, it would be fascinating if you would produce a discrete amplifier for diyaudio based on your AD797.
Luxman preamp C02 circa 1983 , at least for the topology.
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Old 21st June 2013, 09:07 PM   #1046
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Originally Posted by Edmond Stuart View Post
What about the compensation capacitor "Cdom"?
Shouldn't we call it "Ccomp" ?
We could call it Douglas . It is only right .
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Old 21st June 2013, 09:12 PM   #1047
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Originally Posted by michaelkiwanuka View Post

The only snag is shunt compensation to ground increases the non-linearity of the stage it compensates.
Don't see that in practice, or I'm not sure what you mean. All else being equal the input error signal is identicle, and without the symmetry you can't recapture the base current error of the second stage (in the two stage case) without a Hawksford cascode or equivalent.

I have built discrete single stage amps with vanishingly low THD (Ccomp to ground).
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Old 21st June 2013, 09:17 PM   #1048
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Luxman preamp C02 circa 1983 , at least for the topology.
Not even close, that's an ordinary folded cascode tied to V- on the output side. The term and patents appear well prior to the 1983 date.
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Last edited by scott wurcer; 21st June 2013 at 09:29 PM.
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Old 21st June 2013, 10:07 PM   #1049
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Originally Posted by scott wurcer View Post
Not even close, that's an ordinary folded cascode tied to V- on the output side. The term and patents appear well prior to the 1983 date.
Where did i say that there was no prior art.?.

The question was about a discrete design , indeed.

To say that it s not close is somewhat exagerated.
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Old 21st June 2013, 10:15 PM   #1050
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An ostensible improvement to the folded cascode arrangement is apparently due to Shinichi Kamijo:

http://www.ne.jp/asahi/evo/amp/J554K2955/x6amp.pdf

P.S. Wahab, I see you use Simetrix. Good man!

Did you purchase the full version?

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