[Amps] low Q output matching

[Manfred Mornhinweg]

Carel,

> Hi, I was wondering what else, besides bad harmonic suppression, will happen
> when I design my (single band) output matching network (PI-L)  with low Q
> (lowest Q needed to get the match done) ?

I can't really see any problem, except less good harmonic suppression.

But maybe you haven't realized that on the high bands you often have no 
option but to use high Q, because of the tube's internal capacitance. 
The lowest Q you can use is dictated not only by the impedance 
transformation ratio, but also by the sum of the tube output capacitance 
and the circuit stray capacitances in that area. When you push a tube 
with rather high capacitance to a relatively high frequency, you can end 
up forced to use a Q of 20 or 25 or even higher, just to absorb that 
high tube capacitance!

Manfred

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