ST’s Diacs are widely used in consumer appliance applications, such as variable speed hand tools and lighting (in particular CFL), electronic lamp ballasts, electronic transformers for halogen lamps and light dimmers.

Functioning as a trigger diode with a fixed voltage reference, the Diac can be used in conjunction with Triacs for simplified gate control circuits or as a starting element of power oscillators in fluorescent lamp ballasts.
The devices are available in surface mount and axial leaded packages.