>         +24
>          |
>        Load
>          |
>          C
>         /
> PIC-R--B
>         \
>          E
>          |
>         GND
>
> Then the transisor won't be saturated because the 5V output from the PIC
> isn't high enough relative to the collector voltage.

It seems several of your questions come from a confusion about saturation.

This description is a bit over simplistic, but here is the general concept.
For any particular base current, there is a maximum collector current the
transistor will pass.  This is limited by the gain of the transistor.
Saturation occurs when the load on the collector does not allow that much
current.  This also means that the collector is allowed to go to its minimum
voltage (for NPN as shown above).  In fact, the C-E voltage is less than the
B-E voltage for a saturated NPN transistor.  The B-E voltage is that of a
forward biased diode, around 600mV.  The C-E voltage of a saturated silicon
transistor can get below 500mV.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@embedinc.com, http://www.embedinc.com

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