Nicely done.
for anyone not following the point:
The unbypassed cathode resistor always reduces gm. But with a triode, the intrinsic anode resistance ra is increased in proportion to the reduction in gm, and you end up back at a gain of µ, so long as the impedance at the anode is at (or nearly) ra. For low-impedance loads, the gain is also diminished.
with a cascode, ra is almost irrelevant. For a well-implemented cascode, the gain is directly under the control of gm and RL.
for anyone not following the point:
The unbypassed cathode resistor always reduces gm. But with a triode, the intrinsic anode resistance ra is increased in proportion to the reduction in gm, and you end up back at a gain of µ, so long as the impedance at the anode is at (or nearly) ra. For low-impedance loads, the gain is also diminished.
with a cascode, ra is almost irrelevant. For a well-implemented cascode, the gain is directly under the control of gm and RL.
