Understand the working principle of MOSFET and apply electronic components more efficiently

When the gate-source voltage (VGS) of the MOSFET is zero, even with the application of a drain-source voltage (VDS), there is always a PN junction in reverse bias, resulting in no conductive channel (and no current) between the drain and source of the MOSFET. In this state, the drain current (ID) of the MOSFET is zero. Applying a positive voltage between the gate and source (VGS > 0) creates an electric field in the SiO2 insulating layer between the gate of the MOSFET and the silicon substrate, directed from the gate towards the P-type silicon substrate. Given that the oxide layer is insulating, the voltage applied to the gate, VGS, cannot generate a current in the MOSFET. Instead, it forms a capacitor across the oxide layer.

As VGS gradually increases, the capacitor charges up, creating an electric field. Attracted by the positive voltage at the gate, numerous electrons accumulate on the other side of the capacitor, forming an N-type conductive channel from the drain to the source in the MOSFET. When VGS exceeds the threshold voltage VT (typically around 2V), the N-channel of the MOSFET conducts, initiating the flow of drain current ID. The gate-source voltage at which the channel starts to form is referred to as the threshold voltage VT. By controlling the magnitude of VGS, and consequently the electric field, the size of the drain current ID in the MOSFET can be modulated.