I do not think that calling every amplifier with a single input device instead an LTP a CFA is very helpful.
Because datasheets show current gain instead of transconductance. In addition, a lot of textbooks consider Vbe as constant and all the equation are written that way.
Not until I had taken the time to think about it did it hit me. One really has to think about it, instead of just thinking "uh uh" and giving it no more thought.
http://www.diyaudio.com/forums/soli...s-current-feedback-amplifier.html#post3411884
See also post #12 of this linked thread, it gives some names who proved to be undoubltly skilled in using BJT while considering them as voltage driven devices.
I may be a little deficient but I never couldn't understand the explanation of current mirrors mechansims where BJTs are presented as current amplifying devices.
Looking BJTs as driven mainly by the Vbe may be at bit crude but it is the most efficient way to explain and to design audio circuits.
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I agree. My point is that it isn't taught that way in colleges. That's why so many people seem to have a problem looking at it that way. Not that it's the wrong way to see it...
I hope I'm not misunderstanding you, but let me point out that most colleges do indeed teach the operation of the BJT as being a voltage-controlled device with its primary amplifying characteristic as being transconductance. The most well-known model of the BJT is, in my opinion, the hybrid-pi model. That is the model taught in just about every EE class. Central to that model is a transconductance element. The current gain of a transistor is generally quite poorly controlled and is dictated largely by what one might even call a parasitic base current.
Indeed, well-designed circuits perform well as long as beta is large enough. Circuits that depend on beta being a certain value are to be avoided. Circuits that cannot perform properly if beta is too high are especially unreliable.
Cheers,
Bob
Please Doctor Self, tell me the one is the best...were to find the schematic
Because i gonna try it immediately!..... early morning of Saturday.
To me, in my point of view, after thousands of amplifiers built, the Blameless is the only one capable amplifier in the world....if there's a better one i would like to know as soon as possible because i am 53 years delayed related to make the best....i though i have found the best and made the best...your Blameless slighly tweaked.....but if i am wrong i am ready to make the best, to check it, to compare it and to change my style.
In my vision there are many excellent guys in electronics..but you are the best..not doubts about that...you and your amplifier.
I will not take your advise now, only if the circuit is Leach style, because the complementary with matched gain in the input is a hell on earth to obtain matched parts in my place (shops)..it is fully symetrical and has PNP and NPN differential input amplifiers...if this is the style i will build it latter, the day i found the matched ones.
My amplifiers are usually tweaked results from already discovered sub circuits (differential, VAS, EF).... they are Frankstein alike units.... they are for diy, they are not for commercial purposes...and usually they are Blameless style circuit (PNP differential, enhanced VAS, bootstrap or CCS feeded VAS and EF in the output).... i often inform folks i have not created the circuit, that is yours in the origin, that i have tweaked to make it my way.
regards.
Carlos
Because i gonna try it immediately!..... early morning of Saturday.
To me, in my point of view, after thousands of amplifiers built, the Blameless is the only one capable amplifier in the world....if there's a better one i would like to know as soon as possible because i am 53 years delayed related to make the best....i though i have found the best and made the best...your Blameless slighly tweaked.....but if i am wrong i am ready to make the best, to check it, to compare it and to change my style.
In my vision there are many excellent guys in electronics..but you are the best..not doubts about that...you and your amplifier.
I will not take your advise now, only if the circuit is Leach style, because the complementary with matched gain in the input is a hell on earth to obtain matched parts in my place (shops)..it is fully symetrical and has PNP and NPN differential input amplifiers...if this is the style i will build it latter, the day i found the matched ones.
My amplifiers are usually tweaked results from already discovered sub circuits (differential, VAS, EF).... they are Frankstein alike units.... they are for diy, they are not for commercial purposes...and usually they are Blameless style circuit (PNP differential, enhanced VAS, bootstrap or CCS feeded VAS and EF in the output).... i often inform folks i have not created the circuit, that is yours in the origin, that i have tweaked to make it my way.
regards.
Carlos
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I doesn't matter at all what is taught in EE classes what only matters is how in terms of physics does a BJT work.
Most if not all explanations given in EE classes are either incomplete or just dead wrong.
Yet, the people who learn it that way go on to build great amps and equipment. So it can't be all wrong
jan
Many people are convinced that BJTs are amplifying devices because the property of beta is very easily demonstrated. It may be the first experience shown with elementary amplifying devices. Then, the students take the wrong conclusion and retain it as an undoubtful fact.
In France, many quite old people were very angry against me when I defended the point of view of BJTs as being transconductance devices. They even call the great names I quoted "my idols". Many of these great names are writing here or, not anymore among us, very often appear through these lines !
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This is a foolish statement. Where did you get your degree? Speak for your own school.
Cheers,
Bob
Oh I happened to be at IBM R&D where I designed ( at that time) ultra fast
micro CPU with ECL ....
if you don't understand the physics of semiconductors you won't ever get how BJTs function.
Not all wrong, by a longshot, but from my own experience as a EE, I found out much later that most EE classes teach very little about how a device actually works. What they do teach, and very well, is the application and circuit design theory using the various types of devices. At the same time, there is simply little opportunity to delve into the physics.Yet, the people who learn it that way go on to build great amps and equipment. So it can't be all wrong
jan
A few years after the ink on my diploma was dry, I had an opportunity to work with some people who had an applied physics background, and I realized that they looked at the same semiconductor devices in a completely different way. Very few people, in my experience understand both, equally well. Personally, I am happy to use any good ideas, regardless of where they came from...
edit: In other words, mostly look forward to when the new book or books come out... LOL!
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