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:
(a) Breakover voltage
(b)Voltage symmetry
(c) Breakback voltage
(d) Breakover current
(d) Power dissipation |
Typical diacs
that are supplied by American Microsemiconductor
| ELECTRICAL
CHARACTERISTICS (T=25oC) |
| PART NUMBER |
Breakover Voltage
V |
Breakover
Voltage Symmetry V |
Dynamic
Breakback Voltage V |
Breakover Current
ľA |
Peak Pulse Current
A |
|
Min Typ Max |
MAX |
MIN |
MAX |
MAX |
| D30 |
28 32 36
|
3 |
5 |
100 |
2.0 |
| D40 |
35 40 45
|
3 |
5 |
100 |
2.0 |
| ST2 |
28 32 36
|
3.8 |
- |
200 |
- |
| HT32 |
27 -
37 |
3 |
5 |
50 |
2.0 |
| DB3 |
28 32 36
|
3 |
5 |
- |
1.0 |
P. O. Box 104,
133 Kings Road, Madison, New Jersey 07940, Phone: (973) 377-9566, Fax: (973) 377-3078
Questions, Comments, Suggestions - Email To: info@americanmicrosemi.com |
