Quote:
Originally Posted by oldeurope
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Please note this
Quote from STC website:
"I write that the output voltage will be changed, but of course the feedback is not superconductivity(!), so the output has some output impedance.
The value of output impedance is determined by the characteristic of output tetrode.
As I already explained, this is 100% voltage feedback, so it is defined by the trans-conductance (gm) of output tetrode, because it defines the open voltage gain.
Ip of tetrode/pentode is determined by Vgk and proportional constant 'gm' (transconductance);
Ip=gm·Vgk, so Vgk=Ip/gm
So, if the load resitance(or impedance) is RL, the open loop voltage of tetrode;
Vout=RL·Ip
gain of tetrode Av is Vout/Vin. From above two equations;
Av=gm·RL
And thus, the output impedance Ro is determined by 100% feedback,
Ro=RL/(gm·RL) = 1/gm
this is just the same as cathode follower."
Hm, you don't get the typical triode output graph shown at the beginning of the thread. At the input you need the voltage to current converter.
I did not notice this at first look, this thing is very different from the triodelington. The voltage gain is not (much) reduced by the load and the feedback triode works with µ gain
. In a real triode amp and the triodelington you must take a load resistance much higher than the load for maximum output.
Kind regards,
Darius