yup...i did put the schottky diode for the motor. I'm using 1N5819 (1 amp) as I can't get the 1N5822 here. I use 11.1v Li-Po battery for it cause the original DF also use the 11.1v battery and i think the motor is similar right? I have check the voltage across the motor and also the current with multimeter for different PWM frequency.

PWM freq : 1KHz
PWM duty cycle (Full throttle) : 62%
voltage across motor : 7v
current : 7.5A

PWM freq : 10KHz
PWM duty cycle (Full throttle) : 62%
voltage across motor : 6v
current : 5.5A

PWM freq : 20KHz
PWM duty cycle (Full throttle) : 62%
voltage across motor : 5.5v
current : 3.5A


So I choose 20KHz for the freq. the motor is running quite cool, just the MOSFET is hot. Maybe most of the power is dissipated by the MOSFET