The LM431A / LM431B / LM431C are three terminal output adjustable regulators with thermal stability over the full operating temperature range. The output voltage can be set to any value between VREF (approximately 2.5 V) and 36 V with two external resistors. These devices have a typical dynamic output impedance of 0.2 Ω. Active output circuit provides a sharp turn-on characteristic, making these devices excellent replacements for Zener diodes in many applications.