For instance, a MOSFET does not require a resistor between the Arduino and its Gate.
Bipolar transistor gain goes down when saturated,
Quote from: polymorph on Jul 04, 2013, 11:20 pmBipolar transistor gain goes down when saturated,No?
Quote from: polymorph on Jul 04, 2013, 11:20 pmFor instance, a MOSFET does not require a resistor between the Arduino and its Gate.Yes it does, and for the same reason as a BJT, ie. to stop more than 40mA coming out of the Arduino pin.
For instance, the gate capacitance of a 2N7000 is 20pf. If an AVR could not drive 20pf without using a current limiting resistor they wouldn't be very useful, would they?
Assume 3.6ns rise time for Arduino output
No, but that's a 2N7000 is a tiny little MOSFET that can't even handle the same current as an average BJT. TO220 size logic-level MOSFETs (the kind most breadboarding people will use) have a capacitance more in the region of 2uF.As a rule of thumb, in a publicly readable forum where we have no idea what MOSFETs people are going to use, can we pretend that MOSFETs need a current limiting resistor?
2uF? Not likely, maybe 2nF.
(shakes head...)Sorry, but I think there is a problem with your math. When is 2,200pF = 2.2uF?