I’m trying to learn about using mosfets for high current applications and there are a few practical things I don’t understand some are about why they get so hot easily if they are such wonder devices and for now what is the advantage and disadvantage of driving n channel mosfets at high and low sides
Temperature depends on power dissipation and heat sinking.
A MOSFET when on is pretty much a pure resistance, power dissipation is calculated from I-squared-R
like any other resistor. Given knowledge of the dissipation and the heat sink performance you can
calculate the temperature and avoid disaster.
If using PWM you have to worry about switching losses (which will depend on how fast you switch
the MOSFET gates - use a MOSFET driver chip always for high power PWM, they are designed to drive
the highly capacitive gate fast and efficiently.
To switch high side either use p-channel or a high-side driver chip with PWM for a bootstrapped
n-channel high-side switch. For low side use n-channel.
The advantage of using n-channel high side is n-channel devices are inherently 3 times
better due to the 3 times higher mobility of electrons over holes in silicon. This only applies
to silicon. For instance GaNFETs are only available n-channel I believe, so there’s no
decision to make.
The advantage of p-channel high side switching is simplicity and you don’t need PWM and
you can turn the load on at 100% duty cycle. Simple n-channel with bootstrapped
driver limits PWM duty cycle to less than 100% as there must be transitions to generate
the bootstrapped gate supply (a few drivers overcome this limitation though, for instance