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Why is total dissipation of MOSFET smaller than VDSS x drain current?

Latest Updated:01/01/2008

Question:

Why is the total dissipation (PT) of a MOS FET considerably smaller than the value of "drain-source voltage VDSS" x "drain current ID"?

Answer:

Drain-source voltage VDSS is the withstand voltage in the OFF state (VGS = 0 V), not the driven voltage in the ON state.
Since the ON resistance is small, a large current flows, and the MOS FET cannot drive such a high voltage. If drain current ID exceeds the absolute maximum rating, please take measures such as attaching a limiting resistor.
Suitable Products
Power MOSFETs