The on-resistance (RDS(ON)) of a MOSFET is an intrinsic property that causes static power losses and depends upon the inner structure of the MOSFET.
The gate charge (Qgd) affects the switching losses and has to be replenished on every switching cycle, so its effect increases with switching frequency.
Together RDS(ON) and Qgd contribute to the overall losses of a MOSFET and they are often combined into a single number (Figure of Merit – FoM) by multiplying them together. This is an important value for comparing MOSFET performance.
In one of Toshiba’s SiC Snacks, the details of this FoM are explained, and the differences between Gen 2 and Gen 3 devices (80% improvement) are outlined.
You can access the SiC Snack flyer on ‘Optimal RDS(ON) * Qgd below:
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