What is an "Enhanced Mode" transistor and how does it differ from a non-Enhanced Mode one?
What difference could it have in a circuit?
it's usually called enhancement-mode. it deals with the physical fabrication of the device. most mosfets we deal with (bs170, 2n7000, etc) are enhancement-mode. i as far as i know, they're more common in industry as well. i never really seen depletion-mode devices, the compliment to enhancement-mode, in my studies.
the difference has to do with the switching voltage of the gate, as i understand it. i think the gate has to be brought high to cut off the channel.
i don't know how it would sound in a circuit, but they're not drop-in replacements for enhancement-mode devices. you'd have to design a circuits specifically for them.