How to get 6V DC motor running using PWM through STM board
From IRFZ44 datasheet it appears +3v3 won't be enough to drive current for a DC motor. From the typical output plot:



Vgs of +4v5 would drive 8A, considering Vds=9V. Extrapolating the curves you could guess that, with +3v3, Id would be close to 1A or lower. It appears that +3v3 is too low for Vgs threshold. Does connecting gate directly to +3v3 properly drive the motor? Can you measure the motor current in this condition?

You could try using a simple NPN as a buffer for gate voltage, like here:







simulate this circuit &ndash; Schematic created using CircuitLab

Just be aware that in this case the current will flow though the motor when PWM voltage is below ~500mV.

Or you could try these MOSFETs: Mouser - N-MOSFET