TRIAC internal equivalence A TRIAC can be modeled (for understanding conduction paths) as the equivalent of:

Introduction / Context:
Functionally, a TRIAC conducts current in both directions when appropriately triggered. A helpful mental model is to imagine two SCRs connected back-to-back so that each conducts during opposite half-cycles.

Given Data / Assumptions:

• Equivalence is conceptual, not a literal internal schematic.
• Focus is on conduction directions and triggering quadrants.

Concept / Approach:
Two conventional SCRs connected in inverse-parallel allow current flow for both polarities of applied voltage, each SCR handling one polarity. That is the same external behavior that a single TRIAC provides, with the added feature of four-quadrant gate triggering referenced typically to T1.

Step-by-Step Solution:
Consider positive half-cycle: the “forward” SCR conducts when gated.Consider negative half-cycle: the other SCR conducts when gated.Thus, the pair emulates a bidirectional controlled switch—the TRIAC.

Verification / Alternative check:
Datasheet quadrant triggering diagrams mirror those of two anti-parallel SCRs with shared gate control strategies.

Why Other Options Are Wrong:

• Series connection would not give bidirectional conduction with control.
• Thyristor+diode or thyristor+transistor do not reproduce the same four-quadrant characteristics.

Common Pitfalls:

• Assuming a TRIAC is physically two discrete SCR chips; internal structures vary, though the behavior is equivalent.

Final Answer:
Two thyristors in parallel (inverse-parallel connection)