On Sat, Jun 18, 2011 at 6:37 PM, V G wrote: > > If you're using a MOSFET, you don't (and I think shouldn't) use any > resistors. MOSFETs have a very high input impedance and are voltage drive= n. > Drive the gate directly. > > Sort of; They have "infinite" DC resistance but the gate is a capacitor. If you try to make a capacitor go from zero volts to some other value very quickly, yo= u get very high currents. I =3D C*dV/dT The PIC can probably handle switching a small MOSFET gate with no resistor, without causing harm, but it wouldn't be my choice. I would always limit th= e maximum current to the data sheet spec using a series resistor. --=20 Martin K. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .