This is probably the most lame question of all the time here, but… I cannot understad grid-cathode "negative" polarization. For me, grid is always positive to the cathode. I mean, in practice, cathode is just GND or 0V, while grid gets voltage larger than zero and never goes below zero. So how come it has negative voltage comparing to cathode?
Let me show you how I understand a triode operating.
This is the most basic grid-cathode polarisation example and it does make some sense for me. We have reference 0V and this is cathode electron emitter, but we also have a battery connected below zero:
This example "seems legit" – cathode is connected to 0V but grid has own battery that provides voltage which is (theoretically) below zero*.
However, in real life no such battery exists, and there's just one 0V/GND point, common both for cathode and input signal.
What's more, the input voltage changes from 0 to 1V (not from -1V to 0V) in my example, so… how does the tube even work? It should not pass possitive voltages through the grid at all and the tube shouldn't work. But it does:
The resistor is of course the key, however it never drops input voltage BELOW 0V because there is no "below zero" point in the circuit. The ultimate zero is just zero, the same 0V point cathode emitts electrons from.
Or is it and I'm just unable to see it?
*) for me in this example grid voltage is stil positive over the cathode :/