Triggering modes in multivibrators: Multivibrators (astable, monostable, and bistable) can be free-running, edge-triggered, or level-triggered depending on configuration. Evaluate the claim: “Multivibrators must be level-triggered.”

Introduction / Context:
Multivibrators form the foundation of timing circuits. Their operating modes include astable (oscillators), monostable (one-shot), and bistable (flip-flop). Triggering characteristics differ by design, not by an absolute rule requiring level triggering.

Given Data / Assumptions:

• Astable: self-oscillating, no trigger required.
• Monostable: typically edge-triggered to produce a fixed pulse.
• Bistable: toggled by level or edge, depending on implementation.

Concept / Approach:
Claiming “must be level-triggered” is incorrect because many monostable designs deliberately use edge triggering to avoid pulse-width sensitivity on the trigger input. Astables need no external trigger at all, while bistables may respond to either edges or levels depending on circuitry (e.g., debounced pushbuttons feeding edge detectors).

Step-by-Step Solution:

Verification / Alternative check:
Check 555 monostable datasheets: triggering is by a threshold edge crossing, not a static level duration (beyond minimum pulse width).

Why Other Options Are Wrong:

• Correct: Conflicts with standard monostable and astable operation.
• True only for astable/CMOS/50% duty: These constraints do not impose level triggering.

Common Pitfalls:
Assuming “trigger” always means a sustained level; ignoring edge-detection networks; overlooking that different multivibrator types behave differently.

Final Answer:
Incorrect