Switching Characteristics

The switching  characteristics of power MOSFET the delay time and rise time are responsible to remove the  effect of internal capacitance of the device  and internal impedance of the gate  drive  circuit. These  two times  give the  turn on  time of  power MOSFET.

During  the delay  td input  capacitance charges to gate threshold voltage Vgt and during  rise  time td to gate  voltage rises  to V_gp that will  be the sufficient voltage to turn on the power  MOSFET.

During  the turn off  delay  time tod the gates voltage is removed hence  input  capacitance of the device discharges from V_p to V_gp where V_P  is the overdrive gate voltage. The  time during  which this  capacitance discharges from V_gp to V_gt is known  as fall time. In this  time  drain current falls  from IP to zero. Power MOSFET is completely turned off if V_GS < V_gt.