g:gate； S: source source; D: drain. N-channel power supply is generally connected to D, output S, and P-channel power supply is generally connected to S and output D, and the enhanced depletion connection is basically the same.

The transistor has an N-channel, so it is called an N-channel MOS transistor, or NMOS. There are also P-channel MOS(PMOS) transistors, which are lightly doped N-type back gates and P-type sources and drains.

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There are many kinds of MOS transistors, and they also have many functions. For power supply or driving, of course, it is used for switching.

The working principle of both N-type and P-type MOS transistors is essentially the same. The MOS transistor controls the current at the drain of the output terminal through the voltage applied to the gate of the input terminal. MOS transistor is a voltage-controlled device, and the characteristics of the device are controlled by the voltage applied to the gate, so there will be no charge storage effect caused by the base current of triode as a switch, so the switching speed of MOS transistor is faster than that of triode in switching application.

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