Will somebody please help me to understand what is role of millet plateau region in switching of MOSFETs?
MOSFETS have several regions of operation
(1) off, where Vgate_source ~~ zero
(2) on, where Vgate_source ~~ 5 volts or 10 volts
(3) building charge in the gate, as the FET channel charge builds up with opposite polarity inside the region between source and drain
(4) opposite of (3)
During 3 and 4, the input (gate) voltage is minimally changing because the input gate voltage requires lots of charge AND the gate-drain capacitance also requires lots of charge. Unless the provider of that charge is powerful, the oscilloscope shows a plateau.
Where is the charge going? View the FET as an amplifier, perhaps with gain of 10. Thus one volt deltaV on gate produces 10 volts (in opposite direction) on drain. As the gate is charged up (in Nchannel), the drain is moving oppositely and demanding another 10X charge bundle into that gate-drain capacitance.
Unless the gate driver has enormous current ability, there is a hesitation.
In first region, the input pulse charges 2nF + 1nF (the drain remains constant at 50 volts).
In 2nd region, the input pulse charges 2nF + 1nF * (1 + 10) = 13nF, thus slope is 4X slower. With gain of 10 assumed, 1 volt deltaVgate produces 10 volts deltaVdrain in the opposite direction; result is C_gate_drain demands the charge of 11X larger capacitor.
In 3rd region, the input charges 2nF + 1nF.