On Sat, Jun 18, 2011 at 6:45 PM, M.L. wrote: > 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 > driven. > > Drive the gate directly. > > > > > > Sort of; > They have "infinite" DC resistance but the gate is a capacitor. If you tr= y > to make a capacitor go from zero volts to some other value very quickly, > you > get very high currents. > I =3D C*dV/dT > > The PIC can probably handle switching a small MOSFET gate with no resisto= r, > without causing harm, but it wouldn't be my choice. I would always limit > the > maximum current to the data sheet spec using a series resistor. > True, I forgot about that, and his requirement to switch it fast. But wouldn't the resistor then slow down the voltage rise time on the gate? Also, isn't the gate capacitance really really small? --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .