Thank you for your advice. But as far as I know, we can use the nDMOS like that in 3.jpg, not using Mos-diode configuration, but just using the bulk/source drain diode as the Switch. ( Plase seee Page 2 in PDF-file in attachment.) Of course, there is large current at the start time at the first stages,,,... but the maximal instant current just about 25 mA, when Vdd= 12V, is it really so large that it exceeds the Imax? I cannot find the maximum rating of this bulk drain current in data sheets, usually not mentioned.
Confused a lot.