> Especially considering your extreme cost sensitivity, you could use a
> MMBT4401, emitter to ground, base to PIC pin with resistor in series.  Le=
t's
> say you count on a minimum gain of 50.  That means you need a minimum of =
2mA
> base current.  To be pessimistic, let's say the B-E drop is 700mV.  That
> leaves 2.6V accross the base resistor.  2.6V / 2mA =3D 1.3kOhms, so a 1kO=
hm
> resistor sounds about right.  The combination of MMBT4401 and 1KOhm resis=
tor
> will cost a small fraction of a suitable FET.

If going for surface mount an MMBT2222A or (IIRC) PMBT2222A, both SOT-23 ve=
rsions (from different manufacturers, hence different part numbers) of the =
ubiquitous 2N2222A NPN transistor would apply equally well. The resistor va=
lue would stay the same.
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