I've read in the past of issues with Fets getting excessively hot due to not being able to switch off fast enough, as the pic can only sink around 25mA of current, and doesn’t provide a "fast enough" drive circuit for the FET to turn on and off.
For example - the FET takes slightly more time to turn off (or on), and as a result, it will get to its bias point, where it has resistance, and has a voltage drop over it (for this example say its around 5V at this point in time). Now remembering that there’s alot of current (say around 20A) being passed through the FET, its now dissipating alot of power in the form of heat, in this case 5 volts * 20 amps =
100 Watts.
I cant for the life of me find the thread that elaborated on how to build the drive circuit, but from memory, I believe it was something like this;
**broken link removed**
That allows the FET to turn on and off much faster, thus prolonging the life of the FET..
My problem is, how do you know what
resistance the
drive resistor should be