During the MOSFET switching, the gate to source voltage becomes flat during the Vds transition, why is it so? what makes it stay constant?

 During the MOSFET switching, the gate-to-source voltage (Vgs) is used to control the MOSFET, and it is an important parameter that determines the MOSFET's behavior. When the MOSFET is switching, there are two phases: turn-on and turn-off.

During the turn-on phase, the gate-to-source voltage (Vgs) is increased, and this causes the MOSFET to start conducting. The MOSFET's drain-to-source voltage (Vds) decreases as the MOSFET starts conducting, and the voltage across the MOSFET starts to decrease.

During the turn-off phase, the gate-to-source voltage (Vgs) is decreased, and this causes the MOSFET to stop conducting. The MOSFET's drain-to-source voltage (Vds) increases as the MOSFET stops conducting, and the voltage across the MOSFET starts to increase.

Now, during the Vds transition, the gate-to-source voltage (Vgs) stays constant, and this is because of the MOSFET's internal capacitances. The MOSFET has two internal capacitances: the gate-to-source capacitance (Cgs) and the drain-to-source capacitance (Cds). When the MOSFET is switching, these capacitances store and release energy, which causes the gate-to-source voltage (Vgs) to remain relatively constant during the Vds transition.

The gate-to-source capacitance (Cgs) is charged during the turn-on phase, and it discharges during the turn-off phase. Similarly, the drain-to-source capacitance (Cds) is charged during the turn-off phase and discharges during the turn-on phase.

During the Vds transition, the energy stored in the capacitances causes the gate-to-source voltage (Vgs) to remain constant. As the voltage across the MOSFET changes, the gate-to-source capacitance (Cgs) and the drain-to-source capacitance (Cds) store and release energy, maintaining a constant gate-to-source voltage (Vgs) during the Vds transition.

Therefore, the MOSFET's internal capacitances are responsible for the gate-to-source voltage (Vgs) remaining constant during the Vds transition.