Hi,
Normally while controlling motor using the mosfet and PWM why is motor connected on upper above the drain of the MOSFET instead of connecting it to source. What is the main advantage in doing so?

 

Because fets have a high gate to source voltage drop, unlike normal silicon transistors of 0.7v, so its better to use it in the drain side and not as a source follower.

 

Normally it is done because it is easier to drive a low side mosfet. A high side N mosfet takes a high side driver and a boot strap circuit. And N mosfets are more popular than P mosfets, with a bigger selection. Modern mosfets have such a low on resistance the voltage drop doesn't mean much to the circuit.