One-shot (monostable) timing dependencies — which change increases the output pulse width? Assume a standard one-shot whose width t is set by an external R * C network.

Difficulty: Easy

Correct Answer: timing capacitance increases

Explanation:


Introduction / Context:
Monostable pulse width is primarily determined by the product R * C and, secondarily, by internal threshold fractions. Understanding which external parameter directly increases the width is essential in practical design and troubleshooting.


Given Data / Assumptions:

  • One-shot with t ≈ K * R * C, where K is a device-dependent constant
  • Supply-voltage dependence is weak over the rated range


Concept / Approach:
If t is proportional to R * C, then increasing C (or R) increases t, while decreasing either decreases t. Changes to UTP or edges typically do not dominate compared to R and C selection for basic one-shots.


Step-by-Step Solution:

t ≈ K * R * CIf C ↑ then R * C ↑ ⇒ t ↑If R ↓ then R * C ↓ ⇒ t ↓


Verification / Alternative check:
Datasheet curves generally show near-linear scaling of pulse width with timing capacitance across practical ranges.


Why Other Options Are Wrong:

  • Supply voltage increases: often minimal effect on t within spec.
  • Timing resistor decreases: reduces t.
  • UTP decreases: threshold variations have smaller, device-specific effects.
  • Faster trigger edge: affects triggering reliability, not width set by R and C.


Common Pitfalls:

  • Overestimating supply sensitivity for timing; R and C dominate.


Final Answer:
timing capacitance increases

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