Matrix Keypad routine

[passion1]

Steve

Does the same apply to driving a n-channel power mosfet?
I would like to drive a IRFP250N n-channel mosfet.
(for this mosfet the static drain-to-source on-resistance Rds(on)=0.075ohm,
drain-to-source leakage current Idss = 25-250uA)
Do I also need a resistor inbetween the mosfet and the output pin?
If so, should I use the same calc as above to determine the ohm value of the resistor?

[mister_e]

in theory, you don't need any resistor in between as the gate impedance and their gain(not the right term but.. ) is quite large . BUT if you worry of a Gate to Source short, or else weird stuff, you should use a resistor in serie to 'protect' the PIC.

[Ioannis]

... you should use a resistor in serie to 'protect' the PIC.

If your concern is speed then
this res should be as low as possible, 0-470 Ω.
Else
use larger one about 1K
Endif

Ioannis

[mister_e]

I tend to not use any resistor. If i need to drive high current, i sure use something else in between...

[passion1]

Thank you Steve & Ioannis.

Steve, what do you mean with:
"If i need to drive high current, i sure use something else in between..."

[Ioannis]

Another transistor or other driver I suppose.

Microchip has such Mosfet drivers (either for high or los side)

Ioannis

[passion1]

Ioannis / Steve

I would like to drive a 220V circuit with a power mosfet.
Do you think an optocoupler is a MUST or will I be able to get away with a diode to protect my pic?
If so, what diode or alternative protection would you recommend?