TL431 Precision Voltage Reference

A two-resistor adjustable shunt regulator — 1% accuracy from a part that costs a few cents.

Difficulty: Breadboard. Estimated build time: about 30 minutes. Estimated parts cost: about US$1.50. 6-part bill of materials with live supplier pricing. The TL431 is one of those three-terminal parts that keeps showing up in real designs.