Lower threshold LED's

[WGTP]

Are there any that will clip the signal in a feedback loop op amp distortion at about half the typical voltage?  Mine measure around 1.8v.  

[Torchy]

Vf for 3mm & 5mm red leds are 2V (typical). Hi-bri LEDS are higher, often around the 5V mark. I dont know of any LEDS that have Vf of less than 2V.

[bioroids]

I had some leds with a voltage drop of about 1.2/1.4v but I dont know the part numbers (scavanged...) Anyway I think they were the little ones (smaller than 3mm)

Luck

Miguel

[Paul Perry (Frostwave)]

My guess is that the lowest V will be infra red, but I don't think it will be low enough.
You can use a BAT series schottky for a low voltage, but it won't glow of course. neither will an IR if it comes to that..