In terms of operation I assume when the NPN transistor is on there is 0V at the base of the PNP transistor and when the NPN transistor is off there is 10.8V at the base of the PNP transistor.
So my question is why is it that there can be 10.8V (after voltage drop across transistor of course) at the base of the PNP TIP125 when the datasheet says the maximum Base-Emitter voltage can only be a potential difference of 5V?
Also whatever the answer, can the same answer be applied to MOSFETS that also only need 5V?
Because what I'm gathering there's going to effectively be 0v or 12v on the base
and that the base-emitter voltage is effectively always -1.2v for a darlington transistor?
In regards to an npn, can I apply something over 5V from base through to ground?
Also interesting about mosfets needing 3x the threshold voltage, is this fixed? As in always 3x or dependant on the load? Roughly how would you calculate that?
Ok thanks for clearing up some of my knowledge. So what is the significance of the -5V max rating from the datasheet for the base-emitter voltage?
I also notice is says max Vgs is + or -, but the VgsTH is distinctly only negative, why is that?