retrolefty:
That is why I statedexcept most recommend
This is a pretty controversial topic (gate resistor or no for mosfets) around these parts and both parties make a decent case for their point of view. I have mostly not used a series base resistor when driving mosfets with arduino output pins, but then I'm a quick and lazy type that just wants to get some electrons flowing. I'm of the belief that the AVR output pins are pretty husky devices that can take some abuse. But then again I just build hobby projects not selling commercial offerings, so long term reliability is not a high priority for me.
Lefty
Well some MOSFETs are as much as 10nF equivalent input capacitance, and I've don't think I've seen a logic output claim
a max capacitive load more than a few 100pF - so a series resistor is indicated. If the gate capacitance is
smaller (say 300pF or below) then you can argue both ways - the ATmega datasheet doesn't give pin-current derating
curves for short pulses - the abs max current limit might be thermal or it might be ion-migration or both...