[Amps] A Naive Question...

Rob Atkinson ranchorobbo at gmail.com
Fri Jan 13 06:31:58 EST 2023

It's a good question; not naive.  The answer is in the data sheet for
the tube.  For example, take a look at the data sheet for the 3-400.
Let's say we want to drive the grid in class C and modulate the plate
v.  There are "typical operating" sections for various configurations
and conduction angles.  In the section for class C plate modulated
typical operation it says the peak RF grid v. is 185 v. and grid
current is 100 ma.  Using Ohms law we know that the necessary driving
power is 18 watts.  The grid dissipates 20 watts so we're okay.  Even
if you lose your plate v., the grid current will go a little higher
but you'll still be okay.  Let's say we want to design a matching
network to transform the grid impedance to 50 ohms.  To do that we
need to know what the grid impedance is.  Ohm's law tells us the grid
Z is around 1800 ohms for a single tube.


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