[Amps] GG amplifier input impedance

[TexasRF at aol.com]

Another way to look at feed through power is the drive power causes an rf  
voltage to appear between the cathode and ground. This voltage is in series 
with  the plate voltage and the plate power input is raised by the amount of 
the added  cathode voltage. The output power will increase along with the 
input  power.
 
The tube and circuit has a given plate efficiency and that efficiency  
applies to the added cathode voltage. So, it would seem that some of drive power 
 would be lost in the process.
 
73,
Gerald K5GW
 
 
 
 
 
 
 
In a message dated 8/26/2009 2:09:47 P.M. Central Daylight Time,  
ka4inm at tampabay.rr.com writes:

>    Grid to Cathode impedance of a tube
> is the  grid to cathode voltage divided by the
> grid  current!!!

I wouldn't be so quick to say that.   Nothing is that simple.
The load on a grounded grid amplifier  is seen by the amplifier's driver.
(I assume as long as the GG  amplifier is drawing plate current)
A good percentage of the driving power  winds up in the grounded grid 
amplifier's load.
You drive  the cathode, the cathode is connected (through plate 
current) to the plate  of the tube that is connected through matching 
networks etc. to the  load.
-- 
Ron  KA4INM
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