Semi-conductors

[Lance]

I Know how semi-conductors work But I dint know WHY they work.

 

An NPN transistor consists on P-doped silicone sandwiched between two P-doped layers. So assuming that both N layers are the same why are all transistors not bi-polar?

 

Also, all semiconductors have a recovery speed. What determines the recovery speed? How is an ultra-fast diode different than a normal diode?

 

And how do they suddenly fail from overvoltage? Why is voltage so critical?

[YT2095]

both N layers are not quite the same, I gather you`re thinking Emiter, Base and Collector?

what makes one an emmeiter and the other a collector? well it`s to do with doping od the silicon, some materials are still more on the + side of neg than others, that gives then thier bias.

 

recovery speed or Slew Rate, is all about how fast the junction can transfer the electrons across the depletion(sp) zone. different materials will behave in different ways GAs technology is somewhat faster for instance.

 

you mention Non-polar, well such a device exists, Fet`s are reasonably non polar, Igfet, Mosfets, Jugfets etc... they`re still marked up as A.K.G but some species are non polar in the respect that they`ll turn a current on/off without amplification bias, like a simple transitor uses IE/ Emier or Collector follower, one will amp current the other way round it`ll amp voltage.

 

voltage is critical as the junction is delicate, too fast a flow and it`ll break down, the electrons can`t "hop over" the depletion zone fast enough, and if too highly charged it will actualy blow holes in the junction

 

 

now then, it`s been a LOOOOONG time since I`ve done any of this theory stuff, so some of my answers maybe a bit incomplete, some good keywords to look up would be "Depletion Zone" "P N doping" and "Slew rate"

 

that`s the best I can offer atm