Re: pic output port

On Mon, 1 Dec 2003 10:08:31 -0800, "Mike Turco"
<[EMAIL PROTECTED]> wrote:

>How does one calculate the base current required to saturate an NPN
>transistor, such as in the subject circuit?

     The datasheet will usually have graphs of emitter current versus
base current for various voltages.  You can then size the resistor to
get the base current appropriate for the capability of the driver or
the amount of current you want to run through the device.
     I have found mosfets to be better for most applications
controlled by a microcontroller.  The cost difference is less than it
used to be.  The switching current is less and the holding current is
almost nil.  However, I still use bipolars in applications where I
want to block current in both directions or linmit the maximum current
in the controlled circuit.