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[AMPS] Re: [super cathode]

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Subject: [AMPS] Re: [super cathode]
From: gdaught6@leland.Stanford.EDU (George T. Daughters)
Date: Thu, 15 May 1997 14:15:41 +0008
hi all,

> 'Super cathode driven' applies to a tetrode where the
> screen is grounded and the grid is operated at 0 RF-V
> with respect to the cathode.  Thus, there is never any
> grid current in a super cathode driven amplifier
> circuit. 

not necessarily.  'super cathode driven' is where a fraction, call it  "k"
of the driving potential applied to the cathode  is applied to the grid 
as well, thus providing some negative feedback.  if "k" is zero, we have 
normal cathode-driven operation (i.e. the grid doesn't move, the cathode goes
up and down.)  if "k" is unity, the grid chases the cathode up and
down, tracking it exactly.  it is *definitely* true, however, that the 
most reasonable thing to do when using this mode with a 
tetrode is to make "k" equal to unity, i.e. the grid and cathode are 
at the same rf potential, and therefore there is no chance of the 
control grid drawing any current (assuming the tube is biased at a 
reasonable operating point.)

just picking nits....

George T. Daughters, K6GT

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