Duty cycle calculation from timing parameters A periodic digital waveform has pulse width tw = 6 ms and period T = 18 ms. Compute the duty cycle (%) = (tw / T) * 100.
-
A3.3%
-
B33.3%
-
C6%
-
D18%
Answer
Correct Answer: 33.3%
Explanation
Introduction / Context:Duty cycle quantifies the fraction of time a digital signal stays HIGH within one period. It is crucial for pulse-width modulation (PWM), timing analysis, power electronics, and clocking strategies where average power or effective value depends on on-time ratio.
Given Data / Assumptions:
- Pulsed waveform with tw = 6 ms (HIGH time).
- Period T = 18 ms.
- Duty cycle D(%) = (tw / T) * 100.
Concept / Approach:Use the definition directly, ensuring consistent units. Since both times are in milliseconds, unit conversion cancels out. Simplify the ratio and multiply by 100 to get a percentage.
Step-by-Step Solution:
Form ratio: tw / T = 6 / 18.Simplify: 6 / 18 = 1 / 3 ≈ 0.3333.Convert to percent: 0.3333 * 100 = 33.33…%.Rounded to listed choice: 33.3%.Verification / Alternative check:If the pulse is HIGH for 1/3 of the period and LOW for 2/3, average value of a 5 V signal would be about 1/3 * 5 ≈ 1.667 V, which is consistent with a 33.3% duty cycle interpretation in PWM systems.
Why Other Options Are Wrong:
- 3.3%: Off by a factor of 10 (likely decimal-place error).
- 6% or 18%: Confuses pulse width or period with percent; incorrect ratio.
Common Pitfalls:Mixing milliseconds with seconds unnecessarily, or flipping the ratio T / tw. Always confirm that duty cycle is on-time divided by period.
Final Answer:33.3%