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LED (prefer SMT) that will be visible with 1.4Vdc

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Jester

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Single AA battery application. I don't have room for a charge pump

Apparently some GaAs deep red LED's will illuminate with as little as 1.4Vdc.

Digi-Key selection list starts at 1.6V, however this is at 20mA. I don't need the LED to be super bright, just visible when powered from an AA battery.

Can anyone recommend a LED that will be visible with 1.4V, I prefer small (0402) but can live with larger or through hole if those are the only options. Recommendations for series resistor for this situation?
 

possibly Osram LH R974 series, at 1.3V? but it looks like digikey only has 0805

I think Alkaline cells start a little above 1.5V when new. Assume 1.55V (?), then an initial guess for a resistor might be 0.25 V / 0.01A, or 25 ohms.

I expect some trial and error may be involved, though.
 
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    Jester

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Red LEDs are the ones which brings the smallest drop voltages, being perhaps the suited color.

Although alkaline batteries exhibit a smooth discharge profile over time, it sounds not a good idea to use a LED too close of the minimal drop voltage due to the fact that the smallest change in its characteristic would dramatically reduce the its brightness - datasheets specifies a range. In addition, depending on the production lot, and the room temperature, some displacement is expected so that you could not ensure the same intensity of the light to each component.

A voltage doubler could be made with a few amount of components.
 
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