Diac Circuit Diagram. Triac is used in the control circuits such as motor control fan speed controlling light dimmers switching of high power lamps controlling of ac power in domestic applications. Diac circuits tutorial testing.
The above diagram shows the typical construction of the diac. The layers closer to the terminals are the combination of both positive and negative layers. From the diagram a diac unlike a diode resembles a bipolar junction transistor bjt but with the following exceptions.
Diac is used to build different circuits like lamp dimmer heat control the universal motor speed control circuit starter circuits used in fluorescent lamps.
When breakdown occurs the diode enters a region of negative dynamic resistance leading to a decrease in the voltage drop across the diode and usually a sharp increase in current through the diode. In the given circuit diagram a capacitor and a diac is connected in series with the gate terminal of a triac. When breakdown occurs the diode enters a region of negative dynamic resistance leading to a decrease in the voltage drop across the diode and usually a sharp increase in current through the diode. The diac acts like an open circuit until the voltage across the capacitor exceeds its breakover or switching voltage and the triac s required gate trigger voltage.
