There are pitfalls for the unwary with MOSFET datasheets - many are full of graphs of "typical" response.
Unfortunately "typical" isn't very useful as the variation between devices (concerning any gate voltage) is large,
a volt or more, sometimes +/-1V spread, perhaps 20 to 50% in absolute terms.
If you want guaranteed behaviour you have to use the maximum Rds(on) rating, which will specify
a particular gate voltage or voltages - that's a figure you can rely on for all devices across the full
temperature range given.
Another pitfall is not understanding the various gate voltages.
There's the threshold voltage, the point of full turn-off - this is almost never relevant for anything,
so long as its larger than 0V.
There's the plateau voltage, where the main channel forms and the gate charges up (mid way
through switching),
There's the fully on gate voltage, normally taken to be about twice the typical plateau voltage so
that switch on and switch off are fairly symmetrical in time and both rapid and device variation
is allowed for.
Most logic level devices have threshold of 0.5--1.0V, plateau voltage around 2 to 3V.
Most non-logic level devices have threshold of 2.0--4.0V, plateau at 4 to 7V or so
For large loads its common for gate charge and discharge currents to be in the 0.1 to 1A range,
due to the large capacitance between the gate and channel. Feeble gate currents mean very
slow switching, and this can lead to large losses and heat generation.
Although FETs are voltage switched, practical use of a power MOSFET with PWM requires large
gate currents and attention to circuit layout to reduce stray inductance and reduce interference.
This means it very wise to use a gate driver chip to drive the MOSFET gate - its a tough job
so use the component designed for the job. The faster the PWM and the larger the load on the
MOSFET the more important it is to have tight control of the gate waveforms and to have sufficient
gate drive voltage.