I need a design for a constant current source that can deliver a hefty current at around 12 volts with at least 1-2 amps, preferably up to 5. Every current source I've seen uses BJTs or resistors that are submitted to the same current as the load, but I don't want to dish out the money for a 100w resistor or BJT.

I'd like to avoid an LM317, though I'll do it if it's the best option. Is there a good constant current source design that can deliver 12v @ 2-5A using, say, op-amps or mosfets?

The output doesn't need to be perfectly stable, I just want to prevent any components (namely electrolytic caps) from blowing up.

Thanks for any help

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    \$\begingroup\$ Doesn't make sense. Do you want a constant current regardless of the voltage compliance? Or do you want a constant voltage, but to limit the current to a maximum value? \$\endgroup\$ – jonk Jan 13 '17 at 8:46
  • \$\begingroup\$ @jonk Sorry, I can see where that confusion comes from. I want a circuit with a maximum of 12 volts, but the voltage is lowered as needed to maintain a current at or below a set value. Perhaps "constant" current isn't the right term. Current limiting perhaps? \$\endgroup\$ – Daffy Jan 13 '17 at 8:50
  • \$\begingroup\$ @jonk My main issue is that every "constant current" or "current limiting" circuit I've seen online works with at most 20mA which is far too low for my purposes. And they can't be scaled up easily without buying expensive high power resistors or other components. \$\endgroup\$ – Daffy Jan 13 '17 at 8:53
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    \$\begingroup\$ ebay.com/itm/… \$\endgroup\$ – jonk Jan 13 '17 at 9:10
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    \$\begingroup\$ Nah. No need for the points. I'm just glad you found something that will do the job. Doing a switcher (efficient) with spare parts is "hard." Doing a linear circuit is easy, but that's exactly what you said you didn't want to do. So that's that, I suppose. \$\endgroup\$ – jonk Jan 13 '17 at 9:39

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