Current feedback - Voltage feedback, how do I see the difference? - Page 11 - diyAudio
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Old 23rd June 2004, 09:51 PM   #101
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Default 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.
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Old 23rd June 2004, 11:13 PM   #102
mikeks is offline mikeks  United Kingdom
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Default Re: let us come to the point

Quote:
Originally posted by dimitri
....Yes, so called "current feedback" was employed from the beginning of BJT era by injecting the feedback current in emitter of the first stage...........
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....
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Old 24th June 2004, 03:15 AM   #103
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Default 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
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Old 24th June 2004, 04:20 AM   #104
mikeks is offline mikeks  United Kingdom
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Default Re: Yeah, just what the hell is the point????

Quote:
Originally posted by Jocko Homo
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.............
Does anyone remember an occasion marked by Jocko actually contributing anything of value......



http://www.sjostromaudio.com/jocko_homo.html


Quote:
Originally posted by Jocko Homo

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............


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......
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Old 24th June 2004, 05:41 AM   #105
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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.
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Old 24th June 2004, 06:02 AM   #106
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Default 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
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Old 24th June 2004, 06:03 AM   #107
mikeks is offline mikeks  United Kingdom
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Nahhh...

http://www.dself.dsl.pipex.com/ampin...e/discrete.htm
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Old 24th June 2004, 06:09 AM   #108
andy_c is offline andy_c  United States
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Quote:
Originally posted by Nelson Pass
Jeez, you can't say Boo on this site anymore without an
argument about semantics(...)
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."
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Old 24th June 2004, 06:13 AM   #109
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"This abuse. You want argument, next door over."

Jocko
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Old 24th June 2004, 06:37 AM   #110
andy_c is offline andy_c  United States
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Quote:
Originally posted by Jocko Homo
"This abuse. You want argument, next door over."
No it isn't!
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