Remember if you slice the Demrow circuit (1968) down the middle you get the classic transistor/op-amp CFA. I unfortunately called it feedback with enhanced BW property, if I had only known. 😉
Denying evidence. Typical.
I missed the Demrow circuit at the time. 1968, still in elementary school 😀.
I was on the verge of discovering Barrie Gilbert which turned out quite ironic. I agree on letting the CFA controversy go back to sleep before we create some new sockpuppets. What happens when you cross a sockpuppet with a troll?
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That would be a socktroll. Ouch, I bet mike is watching 😀.
I built my first tube audio amplifier in 1970 (mono, ECC83 + 2 x EL34). Didn't like when I got a shock due to a big electrolytic can having poor contact to the painted steel chassis, so the first solid state (germanium) followed in 1971 (classic RCA topology). Designed a TCA790K power audio IC clone as a student, and got it in silicon before the end of the 70's. Sold in the millions for radios and TVs (yes, I "penetrated the home market" 😀).
I was also in elementary school at that time and was building/fixing Tiger and other kit amps and tuners.
No need for another CFA war
Hey guys, I'm really interested in learning if I got it reasonably right or wrong about CFAs in my book. I don't care about who wins or loses a war. A few posts back someone said I didn't get it right. I just asked for a little more information to understand how he thought I got it wrong. I certainly did not want to re-ignite a CFA-VFA war. I was just unable to come to a conclusion that CFAs were better than VFAs. What was I missing, if I was missing something? Did my fairly simple example circuit do a serious injustice to CFAs? I welcome more discussion that elucidates.
BTW, I used what I consider to be CFAs back in 1971 at Bell Labs on the Picturephone transmission system in equalizers that needed to be precise out to 1 MHz. They worked very well in that application.
Cheers,
Bob
Hey guys, I'm really interested in learning if I got it reasonably right or wrong about CFAs in my book. I don't care about who wins or loses a war. A few posts back someone said I didn't get it right. I just asked for a little more information to understand how he thought I got it wrong. I certainly did not want to re-ignite a CFA-VFA war. I was just unable to come to a conclusion that CFAs were better than VFAs. What was I missing, if I was missing something? Did my fairly simple example circuit do a serious injustice to CFAs? I welcome more discussion that elucidates.
BTW, I used what I consider to be CFAs back in 1971 at Bell Labs on the Picturephone transmission system in equalizers that needed to be precise out to 1 MHz. They worked very well in that application.
Cheers,
Bob
I wouldn't worry about this. Strong statements often happen, with zero follow-up or explanation indicating they are based on personal view only.
I think your CFA discussion is quite clear. I had an 'aha!' event realizing, thanks to your fig. 9.18, that, seen from the feedback network, the buffer output resistance Rout is in parallel with R1 (feedback node to gnd), meaning that R1 doesn't shunt any current (assuming Rout<<R1).
For your 3rd Ed. ;-) you might want to expand on difference in bandwidth with gain variation between CFAs and VFAs.
Jan
Yes, a critical feature for audio reproduction
.Bob, check #9532, I believe there’s an error in fig. 9.19
Most go to the Opera to enjoy live performances and music. And some, to hear how the musicians are out of tune.
Good book Bob, one of the best. Thank you..
Good book Bob, one of the best. Thank you..
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Yes, a critical feature for audio reproduction
Bob, check #9532, I believe there’s an error in fig. 9.19
Typical you. First refer to something that was not said, then ridicule it.
Well, we all get off in our own way I guess.
Jan
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And in that light, this may be of assistance (it was indicated by Tournasol (thanks for that))
Nice app note - If you read it in conjunction with Bruno’s ‘F Word’ you get a good feel for CFA.
Yes, and as was 'referred to https://www.diyaudio.com/forums/sol...lls-power-amplifier-book-955.html#post5872349' earlier (by Jan/Bob 🙂) it explains the GBW differences between both (VFB/CFB) clearly (I thought).
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You said it, I was wondering why this property is important for an audio amplifier, in an audio design book. If this is important, may I also suggest a chapter on PCB microstrip design?
P.S. you just said it again, may I ask why this discussion is important in an audio book (instead perhaps quoting relevant material)?
P.P.S.
...which is exactly what I’m trying to convey. Of course, I can hear loud and clear the noise coming from the audio CFA fan club.
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