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You could probably use a Darlington pair if you really wanted, but a MOSFET will do a better job cheaper with fewer components.
Have you done any testing with 1.5 ohm or higher atty loads.I have found that the mosfet circuit using a 1.5 ohm needed tweaking.Being you are not breaking heavy current and using it on the enable (low current) pin, it may not be effected by the load.
Cheaper? From my local surplus: DARLINGTON = 4 resistors at 6 cents, 1 diode at 14 cents, and 1 Dar PNP transistor at 14 cents. = $0.52 cents
Cool thanks for the info.....I have a MOSFET for the circuit used in the Copper Side By Side, Although it is currently lost in parts storage bins.....I guess I should find it and make SURE it is in an anti-static bag.I have moved from breadboard to workbench with this Darlington circuit.... the Case (tube) is going to take a while but, the circuit is performing well....I should be able to take some test tokes from it tomorrow...its 90% built with the last 10% awaiting the case to be finished. I have hooked it up temporarily to make sure its correctly built and working and made initial measurements. Built in free form to plan posted above. So far so good. May design it as a small circuit board for surface mount. at 11 board mounted components it would be too extreme of a build as surface mount. I think I can get all 805's for the resistors, caps, & diode. The transistor: SOT23 and the LDO: TO-263. I won't go smaller than 805....the 603's are too much of a fiddle.
Here some previews....My Comments on my photos: Photo 1: Dang how I am going shove all those electronics into that little tube Photo 2: Its looking kind of Steampunky right now, but Its going to get a coat of paint. Ready for final sanding cleaning and priming.