3.9V 1N4730 1 Watt Zener Diode

A Zener diode works like a normal diode in the FORWARD direction, but when voltage is applied in the REVERSE direction it does something really useful. At a specified reverse voltage it starts to conduct. In other words, if you apply, say 12V (for a 12V Zener) across the diode it will start to conduct current. See diagram: When the Zener starts to draw current, this has the effect of regulating the positive (+) voltage. Note: As the Zener draws current, this will turn into heat. The Zener therefore has a wattage rating (as well as its Zener voltage rating) this may not be exceeded. Jaycar carries a range of Zener diodes from 3.3V to 75V.Fig 1. As positive (+) voltage climbs up to 12 volts the 12V Zener starts to conduct, drawing current