TRIAC triggering polarity A TRIAC can be triggered into conduction by what gate signal polarity?

Introduction / Context:
A TRIAC is a bidirectional thyristor used in AC control applications. Understanding its gate triggering quadrants is crucial for reliable firing in all voltage polarities.

Given Data / Assumptions:

• TRIAC supports conduction in both polarities of main terminal voltage.
• Gate triggering can occur with gate current of either polarity depending on the operating quadrant.

Concept / Approach:
The TRIAC has four triggering quadrants: MT2 and gate can be positive or negative relative to MT1. Practical designs often prefer specific quadrants for sensitivity and noise immunity, but both positive and negative gate currents are possible.

Step-by-Step Solution:
Recognize bidirectional conduction property.Note that gate current of either polarity can initiate conduction when appropriately referenced.Hence, selection: either positive or negative gate signal.

Verification / Alternative check:
Application notes show triggering in quadrants I and III (and sometimes II/IV) depending on gate drive circuitry.

Why Other Options Are Wrong:
Positive only / Negative only: Incomplete understanding of TRIAC quadrants.
No gate signal / Only AC: Not generally correct; a DC pulse is commonly used.

Common Pitfalls:
Ignoring quadrant sensitivity differences (some TRIACs are more sensitive in certain quadrants).

Final Answer:
either positive or negative gate signal