Simple go-to constant current/current limit circuit?

[Deku Tree]

I'm trying to come up with a quick and simple way to limit current to a nichrome burn wire. The wire resistance is about half an ohm. Depending on the wire length it looks like I need around 3-4A. The circuit is powered by a battery of my choice (most likely a small LiPo or Li-ion because that's what I have on hand).
Ideas I've looking in to so far:

• USB current limiting IC
• Other current limited switches like the TPS6528
• Using an op amp like in this article: http://www.bristolwatch.com/ccs/index.htm

The current regulating switches and protection ICs all drop the output voltage when hitting the current threshold. A lot of the other circuits I could find, such as placing a resistor between the output of a 3-terminal linear regulator require a resistor in series with the load.

I'm more or less looking for an "off the shelf" solution, however the current source ICs I could find all stopped about 1A in output. Any guidance would be greatly appreciated.

[mikerj]

The current regulating switches and protection ICs all drop the output voltage when hitting the current threshold.

Because that is the only way you can reduce the current, you can't escape ohms law.  With a heating application like this PWM is a more efficient method of controlling current.

[T3sl4co1l]

Get a switching buck regulator that specifies current mode operation or current-limited output.  Even if it's not an accurate current limit, you should be able to find one that's exactly in your range I think.

Tim

[Deku Tree]

Makes sense, will do! Thank you both your for help.

[HackedFridgeMagnet]

If you can use 2 cells, so between 6-8 volts.

you could use this.
 
the FET was logic level and you would have to think about power dissipation.