About MOSFET driver

Post Time: Jul-06-2024

In contrast to the dual spinning crystal triode, it is generally felt that making the MOSFET conduct does not use an electrical flow, but only requires the GS voltage to be higher than a certain value. It is relatively easy to do this, we mainly need a certain rate.

For the structure of the MOSFET, we can find in the GS, GD, there will be some parasitic capacitance, and the MOSFET drive, in fact, is to charge and discharge capacitance. For the charging of capacitors we only need a current is enough, because the capacitor in the charging moment is equivalent to the capacitor as a short-circuit, this time the instantaneous current will be higher than the general situation value. Therefore, we then select or design MOSFET drive circuit program, the first thing to pay attention to the size of the instantaneous short-circuit current can be provided.

Secondly, NMOS, which is widely used for high end drive, must let the gate voltage exceed the source voltage when it conducts. High-end drive MOSFET in the on-time, the source voltage and drain voltage size is the same, so this time the gate voltage should be 4V or 10V greater than Vcc. If in the same system, want to get greater than Vcc gate voltage, you need to specialize in controlling the voltage circuit. Many motor drivers are composed of charge pumps, it should be noted that we should pick the appropriate external capacitor, so as to obtain sufficient short-circuit current to drive the MOSFET.

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