Thermionic devices/solid state devices/transistors

[RL989]

Hi,
Would anyone be able to explain the difference between these devices, especially thermionic and solid-state (not in terms of their properties but mainly their workings?) Also, did solid state devices replace thermionic and transistors replace solid state?


thanks

[Fizzycyst]

You don’t need to know how transistors or thermionic devices actually operate.
All you really need to know is that thermionic diodes and PN junctions basically do the same thing (control direction of current / act as switches) and thermionic triodes and transistors basically do the same thing (control direction of current / act as switches and also amplify an input).
PN junctions and transistors are solid state devices.
They replaced thermionic devices as they could replicate the functions of the thermionic devices but overcame a lot of the limitations of thermionic devices