Re: Re: let us come to the point
I think what's confusing in this whole thing is that in either CFB or VFB, the signal that got feedback is always voltage.
What matters is the internals of the amplifier. I mentioned this earlier and someone also pointed it out a while ago. in a CFB, the error signal is current and is amplified through a transimpedance amplifier. in a VFB, the error signal is voltage and is amplified through a voltage amplifier.
Once you take that approach, it is quite simple.
at least on paper.
I think what's confusing in this whole thing is that in either CFB or VFB, the signal that got feedback is always voltage.
What matters is the internals of the amplifier. I mentioned this earlier and someone also pointed it out a while ago. in a CFB, the error signal is current and is amplified through a transimpedance amplifier. in a VFB, the error signal is voltage and is amplified through a voltage amplifier.
Once you take that approach, it is quite simple.
at least on paper.
Re: let us come to the point
No....the first stage is a voltage controlled device...(BJT or FET)....
(YES...BJTs are voltage controlled current sources!!)
The feedback divider applies a fraction of the output voltage to the input device's emitter.....,
....where it is subtracted from the input voltage applied at its base......
So-called 'current feedback' amps. are merely an elaboration of the ubiquitous complementary feedback pair (CFP),...
...which no one here (thank goodness!!), has refered to as a 'current feedback' design.....
This surely should settle the matter to everyones satisfaction....
dimitri said:
No....the first stage is a voltage controlled device...(BJT or FET)....
(YES...BJTs are voltage controlled current sources!!)
The feedback divider applies a fraction of the output voltage to the input device's emitter.....,
....where it is subtracted from the input voltage applied at its base......
So-called 'current feedback' amps. are merely an elaboration of the ubiquitous complementary feedback pair (CFP),...
...which no one here (thank goodness!!), has refered to as a 'current feedback' design.....
This surely should settle the matter to everyones satisfaction....
Yeah, just what the hell is the point????
You can configure a so-called "voltage feedback" or "current feedback" to use either voltage-series or voltage-shunt configuration to make either a non-inverting or inverting amplifier.
It seems more like the point is for one of us to ponitificate the same old way....for who knows what reason.
Other than perhaps to show the world how stupid and corrupt Americans, and their corporations, are. For shame!! One of them coined a marketing phrase to make a class of products easier to recognise.
And without checking with him first.
Get over it.
(Apologies to Jan Didden........even if we disagree on this point of contention.)
And since when are BJTs "voltage controlled current sources"???
My text books refer to them as current controlled current sources. Which is why every equation with them uses h_fe * I_b somewhere in it. Looks like current to me............
I guess that they should have checked with you first, eh, Mike?????
Jocko
You can configure a so-called "voltage feedback" or "current feedback" to use either voltage-series or voltage-shunt configuration to make either a non-inverting or inverting amplifier.
It seems more like the point is for one of us to ponitificate the same old way....for who knows what reason.
Other than perhaps to show the world how stupid and corrupt Americans, and their corporations, are. For shame!! One of them coined a marketing phrase to make a class of products easier to recognise.
And without checking with him first.
Get over it.
(Apologies to Jan Didden........even if we disagree on this point of contention.)
And since when are BJTs "voltage controlled current sources"???
My text books refer to them as current controlled current sources. Which is why every equation with them uses h_fe * I_b somewhere in it. Looks like current to me............
I guess that they should have checked with you first, eh, Mike?????
Jocko
Re: Yeah, just what the hell is the point????
Does anyone remember an occasion marked by Jocko actually contributing anything of value......
http://www.sjostromaudio.com/jocko_homo.html
Throw this book in the bin sharpish.....a BJT is a VCCS, with the base current required to either extract or replenish base charge (depending on polarity) as soon as transistor action is initiated by said applied voltage.....
The later is therefore an error that must be accomodated, and not the basis for the device's operation......
Jocko Homo said:
Does anyone remember an occasion marked by Jocko actually contributing anything of value......
http://www.sjostromaudio.com/jocko_homo.html
Jocko Homo said:
Throw this book in the bin sharpish.....a BJT is a VCCS, with the base current required to either extract or replenish base charge (depending on polarity) as soon as transistor action is initiated by said applied voltage.....
The later is therefore an error that must be accomodated, and not the basis for the device's operation......
Jeez, you can't say Boo on this site anymore without an
argument about semantics, which is to say that you're
both right. You can't have voltage without some sort of
current, and vice versa.
Quantum mechanics sez so, and Philosophy sez so (If a man
states an opinion and nobody hears it, is he still wrong?) 😉
pass:/ can't keep his faulty opinions to himself.
argument about semantics, which is to say that you're
both right. You can't have voltage without some sort of
current, and vice versa.
Quantum mechanics sez so, and Philosophy sez so (If a man
states an opinion and nobody hears it, is he still wrong?) 😉
pass:/ can't keep his faulty opinions to himself.
Exactly....
Maybe we should talked in hushed tones about the "E" field that creates the charge.......oh, what's the point, someone will take issue with it.
Jocko
Maybe we should talked in hushed tones about the "E" field that creates the charge.......oh, what's the point, someone will take issue with it.
Jocko
Nelson Pass said:
Reminds me of:
# M= Man looking for an argument
# A= Arguer
"M: I came here for a good argument.
A: No you didn't; no, you came here for an argument.
M: An argument isn't just contradiction.
A: It can be.
M: No it can't. An argument is a connected series of statements intended to establish a proposition.
A: No it isn't.
M: Yes it is! It's not just contradiction.
A: Look, if I argue with you, I must take up a contrary position.
M: Yes, but that's not just saying 'No it isn't.'
A: Yes it is!
M: No it isn't!
M: Argument is an intellectual process. Contradiction is just the automatic gainsaying of any statement the other person makes.
(short pause)
A: No it isn't."
Re: Re: Re: let us come to the point
This should clear any 'confusion'....:
http://diyaudio.com/forums/showthread.php?postid=423522#post423522
No...:
http://diyaudio.com/forums/showthread.php?postid=423668#post423668
millwood said:
This should clear any 'confusion'....:
http://diyaudio.com/forums/showthread.php?postid=423522#post423522
millwood said:
No...:
http://diyaudio.com/forums/showthread.php?postid=423668#post423668
Do any of you think SPICE cares about either types of feedback? Still, it can tell you how a circuit will behave. It doesn't need to know if it's a current feedback circuit or whatever circuit for that matter.
Neither do we. The only reason these names are used is to make communication easier. So that we can all understand each other better..
Hmm, I think that perhaps we should get rid of all these terms altogether since they obviously aren't up to the job
Jam: Could you please respond with an appropriate cartoon?😉
Neither do we. The only reason these names are used is to make communication easier. So that we can all understand each other better..
Hmm, I think that perhaps we should get rid of all these terms altogether since they obviously aren't up to the job
Jam: Could you please respond with an appropriate cartoon?😉
Gee I can't believe there was no disagreement about this factual statement!
That was Copernicus, not Galileo...
Tim
Re: Re: Re: Re: let us come to the point
Mike, it's you against the whole world. You mean that you don't control a transimpedance amp with currents? I believe very strongly that it is current in, voltage out - current feed back.mikeks said:
Re: Re: Re: Re: Re: let us come to the point
SPICE is believed to lead an inanimate existance.....i.e.:...is not generaly considered to be capable of 'care'
Nope...:
http://diyaudio.com/forums/showthread.php?postid=422735#post422735
http://diyaudio.com/forums/showthread.php?postid=422607#post422607
If the amplifier's forward path takes a current as it's input, and delivers a voltage at it's output, (viz: transimpedance gain),.....
.........then major loop feedback applied about such an amp. is a transadmittance....
...since the signal sampled by the feedback network is a voltage,....a fraction of which must be returned as a current before it can be subtracted from the input current to produce the error current needed to drive the amps. forward path....
viz: foward path transfer function= transimpedance
feedback transfer function=transadmittance....
ABO said:
SPICE is believed to lead an inanimate existance.....i.e.:...is not generaly considered to be capable of 'care'
peranders said:
Nope...:
http://diyaudio.com/forums/showthread.php?postid=422735#post422735
http://diyaudio.com/forums/showthread.php?postid=422607#post422607
peranders said:
If the amplifier's forward path takes a current as it's input, and delivers a voltage at it's output, (viz: transimpedance gain),.....
.........then major loop feedback applied about such an amp. is a transadmittance....
...since the signal sampled by the feedback network is a voltage,....a fraction of which must be returned as a current before it can be subtracted from the input current to produce the error current needed to drive the amps. forward path....
viz: foward path transfer function= transimpedance
feedback transfer function=transadmittance....
tsmith1315 said:
that doesn't matter. it is Galileo if we deemed it to be Galileo. History, facts and anything else doesn't matter if it is inconsistent with our conclusion.
🙂
Hey, Mike.......
'Splain this one:
Take one each "voltage feedback op-amp" and "current feedback op-amp".
Try to make a classic integrator with only 3 parts......the op-amp, a resistor, and a capacitor.
Only one will work. Same type of "feedback" applied to each, but one doesn't like it, and oscillates.
Someone......somewhere....who cares on either account........ gives a cute or stupid (take your pick) name to the active device that acts different from everything else that we are used to.
Seems like you are upset because you don't like the name that they picked.
Hey, what's in a name anyway????
Jocko
'Splain this one:
Take one each "voltage feedback op-amp" and "current feedback op-amp".
Try to make a classic integrator with only 3 parts......the op-amp, a resistor, and a capacitor.
Only one will work. Same type of "feedback" applied to each, but one doesn't like it, and oscillates.
Someone......somewhere....who cares on either account........ gives a cute or stupid (take your pick) name to the active device that acts different from everything else that we are used to.
Seems like you are upset because you don't like the name that they picked.
Hey, what's in a name anyway????
Jocko
Jocko,
I can show you a "VFB" opamp that oscillates as well as an integrator. How would you call those? Maybe just call it "opamp unsuitable for integrator", or just "bad design choice"?
Shoot, I *promised* not to post here anymore. Ohh well...
Jan Didden
I can show you a "VFB" opamp that oscillates as well as an integrator. How would you call those? Maybe just call it "opamp unsuitable for integrator", or just "bad design choice"?
Shoot, I *promised* not to post here anymore. Ohh well...
Jan Didden
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