AVR-Chat

Quoting Ryan <g_i_jim2000@yahoo.com>:

> The gate goes straight to an AVR output
>
> --- In AVR-Chat@yahoogroups.com, Robert Adsett <subscriptions@...> wrote:
>> >3) Are there any benefits towards using a "mosfet driver"?  (When
>> >would one be required?)
>>
>> Depends, what are you using to drive it now?

With a logic level device you can get away without anything additional but you
will be pushing the I/O pins hard.  With a non-logic level device you
definitely want a driver.  BTW if the turn-on threshold is above 3V it's a
non-logic-level device.  With a logic level device a high current buffer might
be useful.  Check the pin and device limits on the AVR you are using, 
that will
help choose the gate drive resistor (assume the gate is a short for limiting
calculations)

One thing to watch for is the turn-off, particularly in logic level 
devices. Fast transients on the FET can capacitively couple to the gate 
through the
devices parasitic capacitance turn it on.  Your turn off must be quite 
strong. That's one reason you will sometimes see turn-off and turn-on 
paths to the gate
be non-symmetric.

Robert