article on servo design

[bcarso]

http://www.mobilehandsetdesignline.com/showArticle.jhtml?articleID=207402431

I bridled a bit when I saw the description about eliminating capacitors in the signal path, but calmed down when I read the text and saw what aspects of cap coupling he was concerned about---for example upsetting the input balance of an instrumentation amp due to C mismatch.

I hadn't seen the second-order stuff before as such.

 

[JohnRoberts]

I still find it irritating.. The only way to make a servo without a cap in the path is with a/d convertor, micro, and D/A.... and even then integration is going on, it's just digital... [/rant]

JR

 

[bcarso]

I was ready to complain, but I guess I'm feeling less curmudgeonly these days :green:

At least he didn't prattle about sonic qualities, which was what I guessed when I saw the blurb.

 

[Guest]

Servo is good in case of asymmetrical stages with small gain, but I see no advantages in servo with opamps that have huge DC open loop gain to compensate themselves. hiding caps in amplified feedback don't eliminate them at all, but adds noises and distortions.

"I saw 'Penis' written on the door; but entering there I've found nothing but firewood" (C) Russian saying

 

[JohnRoberts]

I've used them before and there's (some) merit when properly applied.

I object primarily to the mischaracterization with hyperbolic intent.

JR

 

[bcarso]

Part two:

http://www.audiodesignline.com/showArticle.jhtml?articleID=207403101

This time I decided to comment.

 

[JohnRoberts]

Your more diplomatic than I... :grin:

JR

 

[Guest]

I suspect the next article will be called, "Amplifiers with no feedback in signal path", where feedback actually will go through couple of opamps aside of a "signal path".