The red LED provides visual indication of the current flowing through the resistor-zener-diode circuit. The higher the current, the brighter the LED will light. You can omit this LED if you don’t need ...

An uncomplicated circuit application of a ZD is the common shunt voltage regulator. If you have a Zener diode (ZD) of unknown characteristics or if you want to use reverse-biased transistor junctions ...

The circuit is simple enough: it uses a capacitor, a resistor, and a pair of diodes (one of them a zener diode). He uses this basic circuit to drive simple regulators with input and output filter ...