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Re: [Amps] stability of amps

To: amps@contesting.com
Subject: Re: [Amps] stability of amps
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Thu, 27 Sep 2007 21:23:56 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Peter said:
>That design has nothing to do with neutralization, there is none.
ItÂs just passive grid, <


Passive grid relies on the fact that the external impedance from grid to ground 
is less (more?) than any negative real input impedance produced by feedback. 
I'll not go into the argument as to what is a 'negative impedance' - it's taken 
pages of learned magazines without producing any firm definition. For our 
purposes, I'm going to assume that we talk about negative real parts of the 
input impedance. 
Putting it very simply, neutralisation relies on a balance of phase and 
amplitude between the plate to grid impedance and the grid to cathode 
impedance.  Not always easy to get over a wide band
73
Peter G3RZP
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