If you are only using a FET as a switch, a PIC should very easily be able to
drive any logic-level gate type FET
with no problems.

Remember, the gate of the FET is basically a capacitance.  You basically
charge that capacitance up to some gate voltage
which turns on the FET.  For low frequency switching like a basic power
switch, a PIC output is more than enough to drive
the gate of a logic level FET. Even for frequencies approaching a few kHz
you shouldn't have a problem driving a logic
level FET.

The only time when you need additional transistor drivers, MOSFET drivers
(i.e. TC442x etc...) is when you are switching at
high frequency and especially with FETs with a high gate capacitance.  For
example, if you are switching a FET at say 200-300kHz with a 5V output
pulse, you are charging / discharging that gate capacitance relatively fast
and the PIC won't be able to supply the current needed to switch that FET.
Thats when you need additional driver circuitry.

However, for a simple power switch, you don't need anything but a resistor
in series with the gate.  Just make sure its a logic level gate FET.

D



> This application is simply a power switch, so there is no
> high frequency
> switching going on.  In some reference designs I've seen both a mosFET
> driver being used, and in other cases a smaller FET used to
> drive the gate
> on the power device.  So what the better solution, or is there
> one...ie....either one will work, so becomes more of a cost
> issue...whats
> cheaper to manufacture? I know the PIC can't drive it direct,
> that of course
> would be the simpilest and cheapest
>
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