Quote:
Originally Posted by G8HQP Dave
The voltage gain of the lower valve in a cascode is typically around unity, because its anode load is the cathode of the upper valve.
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However, there is no voltage gain from the upper valve, as its cathode and grid are at fixed potentials. And you say there is no voltage gain from the lower valve, then you are saying the circuit has no voltage gain which is not correct. There is voltage gain, provided from the lower valve's gm, because, despite the fact that the plate voltage of the lower valve is fixed, the plate current passes via the upper valve and the load resistance there. And as noted the gain is -gmR, where R is the load resistance. And that gm is the lower valve's gm.