What is DIAC? | Structure, Advantages and Disadvantages

Hello friends, in today’s article I am going to tell you What is DIAC?, the structure of DIAC, working of DIAC, DIAC potential-current characteristics, advantages and disadvantages of DIAC, applications of DIAC: If you also want to know then this article Keep reading the whole so let’s start

What is DIAC?

The term DIAC stands for Diode AC Switch. It is an asymmetric and bi-directional P-N-P-N device. In DIAC, ‘DI’ denotes two-end devices and ‘AC’ denotes alternating current. DIAC is used for triggering TRIAC devices.

1.DIAC construction

The basic structure of the semiconductor layers of DIAC is shown in Figure (i). The DIAC has two ends MT1 and MT2. When the MT1 end is positive to MT2, the structure of the semiconductor layers will be P1-N2-P2-N4. Similarly, when MT2 is positive relative to MT1, the structure of the layers will be P2-N2-P1-N1.
The symbol for DIAC is shown in Figure (ii). The arrowhead indicates that the DIAC can conduct in both directions. The second symbol here is the TRIAC insignia without the gate end. By which also DIAC can be represented.


2.DIAC working principle

is a bi-directional P-N-P-N device that can be started by a positive or negative semicircle of alternating current. For a positive cycle of alternating current, if the value of the applied potential is VBO, then a small current flows through the device, which is called leakage current. This current is generated in the depletion region due to the conduction of electrons and holes and is not sufficient for conduction. For this reason DIAC: experimentally remains in a state of non-operation which is called “Blocking state”. Here the break-over potential of DIAC remains unchanged due to the absence of gate end.

As the value of the applied potential comes close to the break overpotential, the device starts the conduction process and due to this the value of current starts increasing and the value of potential starts decreasing, this field is called conduction on phase.

3. DIAC potential-current characteristic

The characteristic curve of DIAC is shown in the figure. The characteristic curve is found in the first quadrant for positive semicircles and in the third quadrant for negative semicircles.


4.Profits and Disadvantages of DIAC

Merits – DIAC can be used in any direction. For this reason, it is very useful for triggering.
Demerits – This is a low-power triggering device. There is no control unit in it.

5. Applications of DIAC

DIAC is used as a triggering device. As-
(i) in triggering of TRIAC
(ii) in motor speed control
(iii) under temperature control
(iv) in a proximity detector device

Now you must know What is DIAC?, the Structure of DIAC, the Working of DIAC, DIAC Potential-current Characteristics, the Advantages and Disadvantages of DIAC, Applications of DIAC.

2 thoughts on “What is DIAC? | Structure, Advantages and Disadvantages”

Leave a comment