One-shot definition: A monostable multivibrator (“one-shot”) must be externally triggered to produce each output pulse. Is this description valid?

Introduction / Context:
Multivibrators are categorized as astable, monostable, and bistable. Understanding the trigger behavior of a monostable (one-shot) is crucial for pulse generation, timing, and event-counting circuits.

Given Data / Assumptions:

• We are discussing a monostable (one-shot) circuit.
• Claim: each pulse requires an external trigger.
• Standard retriggerable and non-retriggerable variants exist.

Concept / Approach:
Monostable circuits have one stable state and one temporary (quasi-stable) state. A trigger forces the circuit into the quasi-stable state for a time interval determined by RC components (e.g., t = k * R * C), after which it returns to the stable state. Thus, without a new trigger, the circuit will not produce another pulse. Retriggerable designs accept additional triggers during the timing interval to extend the pulse; non-retriggerable ignore triggers until the interval ends.

Step-by-Step Solution:

Verification / Alternative check:
IC one-shots (e.g., 74HC123, 4538) specify triggering modes and show that every output pulse results from a trigger event.

Why Other Options Are Wrong:
Incorrect: Would describe astable behavior, not monostable.

Only true for certain technologies: The trigger requirement is architectural, not technology-dependent.

Common Pitfalls:
Confusing retriggerable behavior (pulse stretching) with astable oscillation; assuming a monostable will repeat without a trigger.

Final Answer:
Correct