chrissugar
Well-known member
A very good paper from the electronic genius, Bob Pease:
http://www.national.com/an/AN/AN-1485.pdf
Enjoy
chrissugar
http://www.national.com/an/AN/AN-1485.pdf
Enjoy
chrissugar
Bob Pease - audio related opamp paper
- Thread starter chrissugar
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AnalogPackrat
Well-known member
Thanks for that link, Mr. Sugar. It is good to know that RAP is still active in op-amps and not just voltage references and voltage to freq converters. I also love how even in 2008 he uses an old analog Tek scope (as evidenced by his beautiful graphs).
Cheers,
A P
Cheers,
A P
Samuel Groner
Well-known member
Thanks, interesting overview. I cannot fully agree with him that the new NSC audio opamps are notably free from thermal effects though--he should have tested the LME49860 at +/-21 V...
Samuel
Samuel
bcarso
Well-known member
Interesting data as far as it goes.
One thing we can control better than ICs is thermal feedback from one part of our circuit to another. And we can get the benefits of matched/coupled parts using multiple transistors where appropriate too---although our choices tend to be shrinking due to part discontinuations.
An area that has received less attention in the audio world at least is thermal feedback from signal-induced self-heating. The 'scope folks had to figure a lot of that kind of stuff out to make fast vertical amplifiers that didn't have low-frequency distortions due to such effects. Tubes had long thermal taus so weren't as much of a bother, though they had plenty of other drawbacks. When teeny transistors had to go fast and needed lots of current to do so, the problem of thermals became crucial.
As often happens in electronics, one field is unaware of the work in another. A French guy has patented some circuit techniques that are ways of coping with thermals in audio amps, calling it memory distortion. Although I don't know that anyone wants to, I suspect the patents wouldn't wirhstand if challenged on the basis of prior art.
One thing we can control better than ICs is thermal feedback from one part of our circuit to another. And we can get the benefits of matched/coupled parts using multiple transistors where appropriate too---although our choices tend to be shrinking due to part discontinuations.
An area that has received less attention in the audio world at least is thermal feedback from signal-induced self-heating. The 'scope folks had to figure a lot of that kind of stuff out to make fast vertical amplifiers that didn't have low-frequency distortions due to such effects. Tubes had long thermal taus so weren't as much of a bother, though they had plenty of other drawbacks. When teeny transistors had to go fast and needed lots of current to do so, the problem of thermals became crucial.
As often happens in electronics, one field is unaware of the work in another. A French guy has patented some circuit techniques that are ways of coping with thermals in audio amps, calling it memory distortion. Although I don't know that anyone wants to, I suspect the patents wouldn't wirhstand if challenged on the basis of prior art.
solder_city
Well-known member
uh oh, bob pease is talking about output impedance
how long before cj starts calling him an *******?
how long before cj starts calling him an *******?
