Diode Droppers - How Do They Work?

A semiconductor diode has an intrinsic forward voltage which is a somewhat complex function of its composition and forward current. The forward current falls off rapidly for forward voltages less than this, and increases rapidly for greater forward voltages. For silicon PN-junction diodes the value is in the 0.7 Volt range, for Germanium diodes, about 0.3 Volts. For silicon Schottky diodes, about 0.5 Volts. LEDs, being diodes also, exhibit this same behaviour, except that their forward (ie, conducting-state) voltages vary as well with the colour of light emitted by the device. IR LEDs, about 1.2 V to UV diodes at about 4.0 volts.

Do you perhaps mean Zener diode?

Try an internet search for Zener diode for more information.

http://wiki.diyfaq.org.uk/index.php?title=Droppers

What do you mean by droppers?

meant for surge protection / over voltage protection in electronic circuits?

Then they must be zener diodes - suddenly drops their Peak reverse voltage to 1.2V when applied little more than their PRV rating.

Are you referring to one of these?

They are diodes that you place under the edison base of an incandescent lamp so the lamp only gets 1/2 wave power. Because there is a residual heating effect in the tungsten element, it still glows, just less so. As a general rule, the lumen output is less than 1/2 so it doesn't really save energy compared to just putting in a smaller wattage bulb. But it does have the benefit of making the bulbs last for years and years. I use them in places where changing a bulb is difficult and dangerous, such as in a staircase.