A 15V 1W Zener diode is a type of semiconductor device that is used to regulate voltage in a circuit. It consists of a p-n junction that is designed to allow current to flow in one direction only, but to also allow a small amount of current to flow in the opposite direction when the voltage across the diode exceeds a certain value, known as the "Zener voltage". This property allows the Zener diode to be used to stabilize the voltage in a circuit and to protect against overvoltage conditions. The 15V 1W Zener diode is a specific type of Zener diode that is rated for a maximum voltage of 15V and a maximum power dissipation of 1W. It is often used in a variety of applications where it is necessary to regulate voltage, such as in power supplies and other electronic circuits. The 1N4744A is a specific model of 15V 1W Zener diode.

A Zener diode is a particular type of diode that, unlike a normal one, allows current to flow not only from its anode to its cathode, but also in the reverse direction, when the Zener voltage is reached.

Zener diodes have a highly doped p-n junction. Normal diodes will also break down with a reverse voltage but the voltage and sharpness of the knee are not as well defined as for a Zener diode. Also normal diodes are not designed to operate in the breakdown region, but Zener diodes can reliably operate in this region.

The device was named after Clarence Melvin Zener, who discovered the Zener effect. Zener reverse breakdown is due to electron quantum tunnelling caused by a high-strength electric field. However, many diodes described as "Zener" diodes rely instead on avalanche breakdown. Both breakdown types are used in Zener diodes with the Zener effect predominating under 5.6 V and avalanche breakdown above.

Zener diodes are widely used in electronic equipment of all kinds and are one of the basic building blocks of electronic circuits. They are used to generate low power stabilized supply rails from a higher voltage and to provide reference voltages for circuits, especially stabilized power supplies. They are also used to protect circuits from overvoltage, especially electrostatic discharge (ESD).