If the period increases, pulse duration will

• A. Decrease
• B. Stay the same
• C. Vary unpredictably
• D. Increase

Answer: (D)

Pulse duration is the length of time the signal stays high within one cycle. It relates to period through the duty cycle: duty cycle equals pulse duration divided by period. So pulse duration equals the duty cycle times the period. If the period grows while the duty cycle stays the same, the pulse duration grows in proportion to the period. For example, with the same duty cycle, doubling the period doubles the high-time of each pulse. Therefore, increasing the period leads to an increase in pulse duration. The other possibilities would require changing how long the signal stays high or changing the duty cycle, which isn’t specified here, so they don’t apply.