Stewart Pinkerton wrote:

On Mon, 13 Dec 2004 21:57:20 +0000, Chris Morriss
wrote:

In message , Sander deWaal
writes
Chris Morriss said:

Yes there is NFB. Consider this: The grid of the triode is fed from a
non-zero source impedance. The signal at the anode is inverted. There
is capacitance between the anode and the grid.

OK?

So we have internal capacitive NFB, which rolls of the gain at high
frequencies. Typical, and expected triode behaviour.

So what would you call it?

Miller effect.


Of course, and the Miller effect has an effect because of............?
(Here's a clue, the words negative, feed and back may just come into it)

Quite so, but it's inherent to the device, so should not IMO be
counted as NFB in a circuit sense, since you don't get the loop delay
problems which occur with global feedback. The same argument of course
applies to the cathode/source/emitter follower, since while there is
100% voltage feedback, there is no current feedback whatever. I don't
count this as NFB, simply changing the mode of operation.

You completely contradict yourself.

You say there is 100% voltage NFB, then you say this isn't NFB.

Global NFB in all amps is series voltage NFB, distinct from the other 3 main
types of FB,
being shunt voltage NFB, series current NFB, and we won't list varieties of
positive FB.

But its a voltage source that we want at the output of our amps, so the only
type of NFB ever used is series voltage NFB, and follower connections
are a prime example of such NFB and its in all the text books
if you don't believe me.

There is no way you can bull**** about "mode of operation", and think that
you'll get away with it.

I believe you are trying desperately to somehow make out that bjts and mosfets

etc are more inherently linear than tubes.

Without NFB, they are very non linear voltage to current devices.




Patrick Turner.



--

Stewart Pinkerton | Music is Art - Audio is Engineering