Vitaliy wrote:
> Olin Lathrop
>> Because heating isn't the only limiting factor on transistor operation.
>> The
>> holes and electrons in the semiconductor material can only move so fast
>> and
>> there can only be so many of them.
>
> This would imply that you won't be able to exceed the Imax (you would
> run out of holes and electrons).

No, it only means that the device characteristics may change to outside the
datasheet parameters.  Also, just like overclocking PICs, you can get away
with it most of the time, but it is not guaranteed operation.  The
manufacturer has to pick parameters that they can hit without excessive
fallout over the whole range of manufacturing variations.

> My point is, the number of minority carriers doesn't constitute a
> "natural" limit where the current physically cannot go above a certain
> limit. You're not supposed to exceed Imax, but it's possible -- just as
> it's possible to exceed Pmax.

I don't think I've ever seen a transistor data sheet that claimed the
transistor had a natural current limit at some value.  Rather Imax is the
value you must not exceed if you want the device to continue operating as
specified in the rest of the data sheet.


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