P-channel MOS transistor switching circuit
The characteristics of PMOS, Vgs is less than a certain value, it will be turned on, suitable for the situation when the source is connected to VCC (high-side drive). It should be noted that Vgs refers to the voltage between the gate G and the source S, that is, the gate is turned on when it is lower than a certain voltage of the power supply, not the voltage relative to the ground. However, because the PMOS conduction internal resistance is relatively large, it is only suitable for low power conditions. High power still uses N-channel MOS tube.
N-channel MOSFET switch circuit
The characteristics of NMOS, Vgs is greater than a certain value will be turned on, suitable for the case when the source is grounded (low-side drive), As long as the gate voltage is greater than the Vgs given in the parameter manual, the drain D is connected to the power supply, and the source S is grounded. It should be noted that Vgs refers to the voltage difference between the gate G and the source S, so when the NMOS is used as a high-side drive, when the drain D and the source S are turned on, the drain D and the source S have the same potential, then The gate G must be higher than the voltage of the source S and the drain D, so that the drain D and the source S can continue to conduct.
