I'll be driving 125mA, so The NDP6060L seems a bit over the top, 48A and the 2N2222 seems more reasonable, 800mA.
Marketing numbers again. Most relevant is the on-resistance (25 milliohms at room temperature). It is overkill for this application (MOSFET's with on-resistance up to 1-2 ohms will be fine for this) but I find it easier to just keep a tub of NDP6060L's around for whatever purpose and not have to think about it. Same thing for the 2N2222 -- 800mA is a hard limit and the device may overheat at that current. Still, fine for 125mA.
The datasheet of the NDP6060L says "Rugged internal source-drain diode can eliminate the need
for an external Zener diode transient suppressor". That is NOT the back EMF suppressing diode is it?
Meh...it could be, but I wouldn't recommend it. The back-EMF diode is supposed to allow current to recirculate in the solenoid coil when the transistor switches off, thus preventing a high voltage at the transistor collector/drain. Without it, the MOSFET's internal diode will avalanche at its rated voltage and will conduct that turn-off current....but diodes are cheap and I'm happier without unnecessary high voltages anywhere in the circuit. Who knows if the solenoid coil is rated for 60V (the minimum voltage at which the NDP6060L avalanches...probably higher)? If it isn't, then the "rugged internal source-drain diode" does you no good because the solenoid could be damaged.
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