Diac

It contains DIAC symbol construction, working, V-I characteristics and applications. I use HP laptop to make PPT. here is link
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1. DIAC Rashmi Patil

2. What is DIAC The term DIAC stands for the  DI ode for  A lternating  C urrent (DIAC), it is a  bidirectional semiconductor switch  that can be turned ON in both forward and reverse direction. The device is a member of the  Thyristor  family and it is mostly used in triggering TRIAC and other Thyristor based circuits. The DIAC starts conducting electric current if the applied voltage goes beyond its break-over voltage. CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA

3. DIAC Packages DIACs are available in  different types of DIAC packages  such as discrete components in small leaded packages, surface-mount packages, large packages that are bolted to chassis and various other packages. Most of the time the DIAC and TRIAC are used together, so they are available in integrated packages also. CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA

4. DIAC - Symbol DIAC is given by the symbol of two  Diodes  connected in parallel and opposite to one another and has two terminals. Since the DIAC is bidirectional, we can’t name those terminals as anode and cathode, the  terminals of DIAC  are simply called A1 and A2 or MT1 and MT2 where MT stands for Main terminals. Hence the  pinouts of DIAC  are reversible just like a resistor or ceramic capacitor. CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA

5. DIAC - Symbol You could have noticed,  although it belongs to the thyristor family it  does not have a controlling gate terminal  because they can be turned on or off by simply reducing the voltage level below the  avalanche breakdown voltage  and it can be done in both the polarities. CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA

6. The above diagram shows the typical  construction of the DIAC .  As mentioned earlier the DIAC has two terminals namely MT1 and MT2 and it can  deliver current flow in both directions .  The DIAC is made of a five-layered structure; the layers closer to the terminals are the combination of both positive and negative layers. When the voltage is passed to the terminals the layer with respective polarity to the voltage gets activated, this combination of both the polarities helps in operating the DIAC in both the directions CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA

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8. DIAC working Principle The above image shows the clear operation of the DIAC with respective to the polarities. Consider the MT1 terminal to be positive, then the P1 layer near MT1 will be activated, so the conduction will be taking place in the order of P1-N2-P2-N3. When the current is flowing from MT1 to MT2 the junction between P1-N2 and P2-N3 are Forward Biased and the junction between N2-P2 is reverse biased. Similarly, if we consider MT2 terminal to be positive, then the P2 layer near MT2 will be activated and the conduction will be taking place in the order of P2-N2-P1-N1. The current will be flowing from MT2 to MT1 and the junctions between P2-N2 and P1-N1 are forward biased and the junction Between N2- P1 is reverse biased. Hence the conduction will be possible in both the directions.

9. VI Characteristics of DIAC Initially, the resistance of the DIAC will be higher because of the Reverse Bias junction between the layers so there will be  small leakage current  flowing through the DIAC, it is mentioned as the  blocking state  in the curve. Once the applied voltage reaches the breakdown voltage the resistance of the DIAC drops abruptly and then it starts conducting which leads to a sharp decrease in voltage and the current starts increasing, which is mentioned as a  conduction state  in the curve. Most of the DIACs will be having the breakdown voltage around 30 Volts, the exact breakdown voltage will be based on the type of the device.   The DIAC will be in the  conducting state  until the current reaches the particular value called the  holding current , where holding current is the minimum current that required for a device to keep it in the ON state.

10. Applications of DIAC The  DIACs are used for triggering TRIAC  or other kinds of thyristors , apart from this they do not possess many applications. The DIACs are used as a trigger device in various applications such as  Phase control circuits of motor speed control, light dimmers, heat controls , and many other control circuits. Let’s look into the examples of Light Dimmer and heat control circuits. CLICK ON TO PURCHASE HP LAPTOP https://amzn.to/2TB8ROA