1N4747A is a 1 Watt Zener diode with a 20V breakdown voltage. It is packaged in a DO-41 (ST) package, which is a standard axial leaded package. The 1N4747A is used in applications such as voltage regulation, voltage reference, and overvoltage protection. It can also be used in series with a resistor to create a voltage divider.(For reference only)