Datasheet in PDF for the Si4128DY, a part number in the Vishay Siliconix power MOSFET range in an SO-8 package, 183 KB. Technicians check pinout, channel type, voltage and current ratings, on-resistance and gate threshold here before testing or substituting the transistor in a power stage. Laptop boards often use such MOSFETs for load switches and DC-DC converters. Confirm the marking on the component matches, and choose any replacement with equal or better ratings in the same package.
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