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Re: [Amps] Designing the Cleanest Linear with RF Negative Feedback

To: Tom Cathey <>
Subject: Re: [Amps] Designing the Cleanest Linear with RF Negative Feedback
From: Gary Schafer <>
Date: Thu, 15 Dec 2005 12:16:19 -0500
List-post: <>
Hi Tom,

Put the resistor in series with the input coupling capacitor.

If you want to experiment with negative feedback with multiple GG 
drivers you might try link coupling between stages. You can reverse the 
link at the feedback point to get the out of phase signal. You will need 
at least a 2 stage amp to do this. Maybe an 811A in GG as a driver for 
the 4-1000.
Put a small coil at the bottom of the input link of the 811A to lift it 
slightly above ground. Couple the plate of the 4-1000 to that point 
through a small capacitor.

Gary  K4FMX

Tom Cathey wrote:
> Correction:
> It was pointed out to me that the cathode resistor for negative feedback is 
> to be used only for a grid driven [grounded cathode] amplifier to generate 
> degenerative [negative] feedback.
> In a cathode driven [GG] amplifier, the cathode is in phase with the plate 
> and it will not work. A different method must be used for neg feedback.
> This is why my GG triode did not show any diffence in drive when I  tried 
> the cathode resistor.
> I saw the idea in the archives and must have missed the fact that they were 
> talking about grid driven amps at the time.
> 73,
> Tom, K1JJ 
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