DIAC
| The diac is a bidirectional trigger diode which
is designed specifically to trigger a triac or SCR. Basically the diac does not conduct
(except for a small leakage current) until the breakover voltage is reached. At that point
the diac goes into avalanche conduction also at that point the device exhibits a negative
resistance characteristic, and the voltage drop across the diac snaps back, typically
about 5 volts, creating a breakover current sufficient to trigger a triac or SCR. A
typical characteristic is shown below with its schematic symbol:
Although most diacs have symmetric switching voltages,asymmetric diacs are available. Typical diacs have a power dissipations ranging from 1/2 to 1 watt. The main characteristics are: |
