I recently found a bag of 3N128's at a yard sale, coincidentally, a couple days after I saw this video on YouTube about controlling a 12V motor with a mosfet, car battery, and arduino:
https://www.youtube.com/watch?v=Lzxuro0Z2Ew
What I'm unsure about is if I can use these as a direct substitute for the mosfet he used. It has 4 legs and the symbol that I found on the datasheet looks a little different than what he used:
http://html.alldatasheet.com/html-pdf/108468/ETC/3N128/110/2/3N128.html
I'm tempted to just connect (4) to (2).