[Amps] Super Cathode Driven Tetrodes

[Ron Youvan]

On 10/28/18 20:40, Fuqua, William wrote:

     Now that this discussion has gone on for some time, and everyone 
has had a opportunity to read various articles, here is the question.

Can anyone give me a reason why a cathode driven tetrode with the 
control grid connected directly to

the cathode be unstable. The screen grid is connected directly to 
ground. Lot mu grounded grid configuration.

> Sorry for typo error. Low mu.

> There should be no reason for this configuration be any less stable that the usual high-mu triode grounded grid

> amplifier, if fact should be more stable due to lower gain.


   I am not experienced with such non-normal tetrode usage, but it occurs
to me that the screen grid (being much closer to plate) being misused in
this way can have greater gain than the control grid in many tubes, like
the suppressor grid in the 6AS6 pentode has more gain than the control
grid.  If so, the miller effect would be much greater.
-- 
   Ron  KA4INM - Youvan's corollary:
                 Every action results in unwanted side effects.