||diac|| definition || construction || symbol || application ||



Diac is important device used to triggered triac. Called as triac without gate terminal due to typical construction.

Construction of DIAC:-
Diac basically two terminal device. It is such a combination of semiconductor layers that allows ori to trigger in both directions. DIAC used triggered for triac.

Semiconductor leyers show in Diagram. There are two terminals MT1 (main terminal 1) and MT2. (main terminal 2).

P1 - n2 - P1 - n1, which is equivalent to an SCR.

MT1is Anode one and MT2 is Anode two.
the equivalent circuit of diac is two scr connected back to back to form DIAC

Diac is a unidirectional or bidirectional device.  This question is always asked.  But Diac is a unidirectional device.

DIAC symbol:-

I-V characteristics of DIAC:-


  • Lamp dimmer. 
  • Fan speed regulator. 
  • Temperature controller. 


  • Low power device. 
  • Dose not have control terminal. 
Request :
Please Sher and comment. 

Satish jagtap

Hello iam Satish jagtap Electrical engineer. From: Aurangabad, Maharashtra. Edu: MIT college of Engineering.

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