A TRIAC is a three-terminal semiconductor device that is notable for being bidirectional, meaning it can control current in both directions.

Key Characteristics

• Bidirectional Control: Unlike the SCR, a TRIAC can control current flow during both halves of an AC cycle, making it highly effective for AC power switching.
• Structure Analogy: Its construction can be thought of as two SCRs (thyristors) connected back-to-back.
• Common Applications: It is ideal for low-power AC applications, including residential light dimmers, small electric fans, and motor controls.

The AC Switching Trade-Off

The main benefit of a TRIAC is its efficiency in AC switching for low-power uses, as it utilizes both halves of the AC waveform. However, its primary drawback is that it can exhibit non-symmetrical switching, which can cause electromagnetic interference in high-power applications. For this reason, it is typically reserved for less demanding roles.

While the SCR and TRIAC are part of the thyristor family, our next device belongs to another major category: the transistor.