MarkT:
The first device must be a common-source stage, with a drain load resistor to the +12V rail (something like 1k perhaps). This will level convert from 5V to 12V (and invert the logic). This can then drive the second devices gate at suitable levels to actually turn it on.
This looks like the right circuit to drive a 12V 3A load for my project (LED ribbon). Can I drive the load at 2Khz (switch on/off 2000 times a second) with this circuit, without wrecking the FET?
Also, are there alternatives to this circuit, e.g. a single component that integrates an equivalent of this whole circuit into it -- logic-controlled high-amperage 12V amplifiers in a single package? (even if a few dollars extra)
EDIT -- Found a ready made multiple-channel Arduino amplifier board suitable for 12 volt control.
http://www.elechouse.com/elechouse/index.php?main_page=product_info&cPath=&products_id=1812