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Old 18th March 2013, 11:19 PM   #101
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Originally Posted by Bonsai View Post
But VFA bandwidth and rise time is inferior to CFA.
No.
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Old 18th March 2013, 11:23 PM   #102
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Originally Posted by michaelkiwanuka View Post
To reiterate:
1) There is no need for excessive bandwith in audio applications.

2) "CFAs" deliver significantly poorer linearity than VFAs.

3) "CFAs" deliver poorer PSRR than well designed VFAs.

4) There is no need for servos with well designed VFAs; this not true of "CFAs".

There is no conceivable excuse for using "CFAs" in audio applications.
Completely wrong!
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Old 18th March 2013, 11:32 PM   #103
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Old 18th March 2013, 11:49 PM   #104
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Originally Posted by michaelkiwanuka View Post
No.
Yes. You can only achieve higher SR and BW by going for MIC, or if non MC, some suboptimal comp scheme. And, whatever scheme you choose, VFA's always require more circuit complexity.
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Old 18th March 2013, 11:55 PM   #105
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Just why would you want more bandwidth or slew than you need?

And what on earth is MIC?

It is relatively easy to design a VFA with 100V/uS slew rate using two pole compensation.

Last edited by michaelkiwanuka; 19th March 2013 at 12:01 AM.
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Old 19th March 2013, 12:00 AM   #106
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....VFA's always require more circuit complexity.
No.
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Old 19th March 2013, 12:01 AM   #107
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There is no need for excessively low distortion in audio.

CFA's easily deliver distortion orders of magnitude below the threshold of hearing, and at least 2-4 orders of magnitude lower than speakers and analog source material (specifically vinyl)

CFA PSRR is below audibility threshold, and is in any event easily solved with simple supply rail filtering

I have no servos in my two current CFA designs as the DC performance is very good ( under 5mV offset). Both designs are fully DC coupled.

VFA's tend to be more complexed expensive than CFA's and yet offer no audible benefit
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Old 19th March 2013, 12:11 AM   #108
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There is no need for excessively low distortion in audio.
There is no such thing as "excessively low distortion".
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Old 19th March 2013, 12:15 AM   #109
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Completely wrong!
Point 3 I think was correct (PSRR).
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Old 19th March 2013, 12:21 AM   #110
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Originally Posted by michaelkiwanuka View Post
Firstly, there is no need for an excessively large closed loop bandwith (say, greater than 2Hz~200KHz) in audio applications.
I have to disagree with the above statement. An amp with 200khz at the canonical -3db does introduce phase shifts in the audio band and is therefore sub-optimal.
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