The LM431SAI is three terminal output adjustable regulator with thermal stability over operating temperature range from -40C to +85C. The output voltage can be set any value between VREF (approximately 2.5 volts) and 36 volts with two external resistors. This device has a typical dynamic output impedance of 0.2 Active output circuit provides a sharp turn-on characteristic, making this device excellent replacement for Zener Diodes in many applications.