[sdiy] Tubes in Spice ?

[Michael Buchstaller]

Hello group,

this weekend i decided to give the circuit simulation with Spice
another try. I tried the B2Spice editor package, as it comes
complete with some common tube models.

As long as i stay with the grid voltage within the usual limits, it
woks ok and gives results as expected. But i want to grossly
overdrive the circuits to see what happens.
But, when i bould a simple amplifier, i note that there is negative
output when whe grid voltage is higher than the cathode voltage.
This happens with all included tube models. Even when i replace
it with ones downloaded from the fabulous DuncanAmps page,
this happens, too.

When i replace the tube with a transistor, it works fine; no negative
output voltages.

Am i doing something wrong here ? Or are there any models that
do behave correctly ?
Please forgive me, but i am not deep enough into spice modelling to
know how to create a new model with the characteristics i want.

Maybe someone has a fully working triode model ?


-Michael Buchstaller