For the 2N7000: R_DS = 2.3 Ohm V_GS=3.3V R_DS = 1.6 Ohm V_GS=5V So at least at 3V3 it's more than an order of magnitude better than the PIC output drivers. RC time is (* 2.3 0.45) 1uS. I guess that's good enough. Let's try a couple more to see the variability. 6.3 4.1 6.3 2.3 Looks like the first one was a good one.