A triac is a three-terminal semiconductor device composed of two thyristors connected in parallel. It can switch alternating current power in both directions by triggering its gate terminal. It has four operating modes depending on the polarity of the voltage applied between its main terminals and the polarity of the gate signal. Triacs are commonly used for AC power control applications like lamp dimmers due to their ability to conduct current in both directions.

1. TRIAC
Triode for alternating current

2. INTRODUCTION
Triac is a three-terminal semiconductor device that is used for controlling the
flow of current. It is commonly used in AC power control applications. A triac
can switch AC power to a load in either direction. It consists of two thyristors
connected in parallel, with the gate of one connected to the main terminal of
the other.

3. T R I A C S Y M B O L
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4. C O N S T R U C T I
O N O F T R I A C
Two SCRs are connected in inverse parallel
with gate terminal as common.
Gate terminals is connected to both the N
and P regions.
It consists of three terminals: main terminal
1(MT1), main terminal 2(MT2), and gate
terminal G.
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WORKING
o There are four different modes of operations, they are-
1. MT2 is positive with respect to MT1 with a gate polarity positive with respect to MT1.
2. MT2 is positive with respect to MT1 with a gate polarity negative with respect to
MT1.
3. MT2 is negative with respect to MT1 with a gate polarity negative with respect to
MT1.
4. MT2 is negative with respect to MT1 with a gate polarity positive with respect to
MT1

6. VI CHARACTERISTICS OF TRIAC
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ADVANTAGE
o It can be triggered with positive or negative polarity of gate pulses.
o It requires only a single heat sink of slightly larger size, whereas for SCR,
two heat sinks should be required of smaller size.
o It requires single fuse for protection.
o A safe breakdown in either direction is possible but for SCR protection
should be given with parallel diode.

8. USE OF TRIAC
1.They are used in control circuits.
2.It is used in High power lamp switching.
3.It is used in AC power control.

9. THANK YOU