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Re: [Amps] High C out

To: vic@rakefet.com
Subject: Re: [Amps] High C out
From: Dennis12Amplify@aol.com
Date: Fri, 21 Jan 2005 14:03:41 EST
List-post: <mailto:amps@contesting.com>
 
In a message dated 1/21/05 12:49:50 PM Central Standard Time,  
vic@rakefet.com writes:

Nope,  he's talking about adding some inductance between the plate and the  
tune-C, making a kind of "L-Pi" (or L-Pi-L!) network.  The idea is  that with 
very high plate load impedances it may be impossible to get a  low-enough 
minimum 
capacity in the tune-C to permit a reasonably low  Q.  Adding some inductance 
before the Pi network pre-transforms the  load impedance to a lower value so 
a 
practical capacitor can be  used.



I agree.
 
 He's creating a two stage impedance transformer.
 
 I'm sorry but I consider a Pi network a Pi network no matter which  end is 
connected to where; and I know that the large C is on the low impedance  side 
of the impedance transformer. I did't realize I was in error calling it a  Pi-L 
network instead of an L-Pi network, but I guess I can see where some may  get 
confused. I DID state that the PLATE C became the new TUNE C in  that 
configuration.
 I have used it myself in some cases to UP-CONVERT impedances to  obtain a 
reasonable tank Q.
 A good example being multiple sweep tubes in parallel where the total  plate 
capacitance is greater than 50 PFD. I have also used similar  circuitry to 
match the Collector impedance from the output of a single  ended transistor 
amplifier before we started using broad band transformers to do  the impedance 
matching, but once again that was for converting a low impedance  to a higher 
one.
 
Dennis O.
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