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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 14th February 2013, 09:53 PM   #35081
john curl is offline john curl  United States
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Read the Solomon article and all will be revealed!
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Old 14th February 2013, 10:06 PM   #35082
Esperado is offline Esperado  France
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John, too much work to translate hundreds of pages, not responding directly to my questions, for the little i had read, even included in my question considering the all closed loop behavior.
Reformulating with an image, reducing gm of the input stage increase the efficiency of the ABS, but not the tire's grip.

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Old 14th February 2013, 10:23 PM   #35083
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
I'd wager "differential mode."
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Old 14th February 2013, 10:32 PM   #35084
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I'd wager "differential mode."
Witch gives some advantage to bridged amplifiers.
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Old 15th February 2013, 01:02 AM   #35085
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Pages 9 and 10 Esperado. You might just learn something.
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Old 15th February 2013, 01:50 AM   #35086
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I thought it was "Dr. Lube"
Maybe it should be Dr. Cremlon, as another branch (one of hundreds) of his company now markets that product.
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Old 15th February 2013, 02:21 AM   #35087
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John Curl's Blowtorch preamplifier part II
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Originally Posted by SY View Post
I'd wager "differential mode."
yes! So now with that knowledge, how do you design a power supply that minimizes diff-mode changes?
What characteristic would it have and what type of circuit has that characteristic?

-Richard
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Old 15th February 2013, 02:30 AM   #35088
john curl is offline john curl  United States
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Here is page 9 (out of 20) of probably the best app. note on amplifier design that I have ever found. The top equation (20) is the KEY EQUATION for understanding slew rate and how to improve it. The left hand term is the definition of Slew Rate, or dv/dt
is proportional to 1/Gm of the input stage. The other terms are related to the input stage operating current and the gain bandwidth of the amplifier.
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Old 15th February 2013, 02:32 AM   #35089
Esperado is offline Esperado  France
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Originally Posted by john curl View Post
Pages 9 and 10 Esperado. You might just learn something.
The truce was short-lived.
As i said, i had read-it, ant nothing new, neither respond my question.
Yes, degeneration increase slew-rate of the input stage, thus a part of the delay. But the issue*is* the closed loop and it does the contrary of what we want : each stage faster than the previous one inside the loop.
You prefer open loop topology and you seem to allow artificial enhancement of slew rate *by the feedback* ? Seems contradictory.
CFA is a way to achieve high bandwidth of the first stage, *by design*. It does not replace having a fast power stage, where current is most demanded and load non mastered..

Last edited by Esperado; 15th February 2013 at 02:43 AM.
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Old 15th February 2013, 02:34 AM   #35090
Esperado is offline Esperado  France
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how do you design a power supply that minimizes diff-mode changes?
Virtual ground ? (Does not work so good because distortion.).
An other solution (don't know the word in English) is crossed feedback between the two sides.

Last edited by Esperado; 15th February 2013 at 02:53 AM.
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