[Amps] GG amplifier input impedance

[Ron Youvan]

>    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