QJxx40xx Series, TRIACs

Thyristors are electronic devices that conduct AC (alternating current) in a single direction or one half of an AC cycle. By contrast, a TRIAC (triode AC) conducts current in either direction when its gate is triggered. Also known as bidirectional triode thyristors or bilateral triode thyristors, TRIACs come in several different types, including snubberless, alternistor, internally triggered, logic gate, and standard, which can be chassis-, surface-, or through-hole mount. When selecting a TRIAC, the key parameters to consider include the off-state voltage, on-state current, hold current, and gate trigger voltage. These specifications will determine the specific applications for which a particular type of TRIAC is best suited. The snubberless TRIAC is designed to operate without requiring a snubber network to protect against voltage spikes and other electrical disturbances. Alternistor TRIACs are optimized for use in circuits with highly inductive loads, such as motor control and lighting applications. Internally triggered TRIACs are activated by an internal circuit, whereas logic gate TRIACs are controlled directly by digital logic signals. Standard TRIACs are the most common type and are appropriate for many different applications. TRIACs can be mounted on different types of circuit boards, including chassis-, surface-, or through-hole mount. The choice of mounting type will depend on the specific requirements of the circuit design. In summary, TRIACs are bidirectional triode thyristors that can conduct current in either direction when triggered. With several different types available, each optimized for specific applications, selecting the right TRIAC requires careful consideration of parameters such as off-state voltage, on-state current, hold current, and gate trigger voltage.