What sets the pulse width of a one-shot (monostable multivibrator)? Identify the primary factor controlling the output pulse duration.

Introduction / Context:
One-shot (monostable) circuits produce a single, fixed-duration pulse when triggered. Most logic one-shots and timer ICs set that duration using a resistor-capacitor (RC) timing network. This question checks identification of that governing factor.

Given Data / Assumptions:

• Monostable topology with a timing node connected to R and C.
• Triggering mechanism initiates the timing interval.
• Device families (e.g., 555, 7412x) employ RC-dependent internal comparators.

Concept / Approach:

Pulse width t_w is proportional to RC, with a family-specific constant (for example, 555 monostable uses t ≈ 1.1 * R * C). The clock characteristics typically do not set t_w directly in a monostable; they only determine how often triggers arrive.

Step-by-Step Solution:

Verification / Alternative check:

Design guides recommend changing R or C to tune pulse width; timing equations in datasheets directly reference RC products and not the external clock width.

Why Other Options Are Wrong:

Clock frequency and pulse width of the trigger (a, b) determine triggering rate and edge qualification, not the monostable duration. An RL time constant (c) is unrelated to standard logic one-shot timing networks.

Common Pitfalls:

Confusing one-shots with pulse stretchers conditioned by input width; assuming the trigger length must equal the output pulse width.

Final Answer:

an RC time constant