In pulse and switching waveforms, what is the name for the time it takes a pulse to fall from 90% to 10% of its maximum amplitude?

Introduction / Context:
Timing parameters characterize how quickly digital or analog signals transition between levels. Standardized definitions use percentage points to avoid noise near the extremes. Recognizing the correct term for the downward transition is essential in waveform specs and data sheets.

Given Data / Assumptions:

• We consider a pulse falling from a high level to a low level.
• Measurement points are 90% and 10% of the maximum amplitude.
• Standard positive logic conventions apply.

Concept / Approach:

The time from 10% to 90% during a rising edge is the rise time. The time from 90% to 10% during a falling edge is the fall time, also called the decay time in many texts. Propagation delay refers to the time between input stimulus and output response (e.g., tPLH, tPHL), not the edge slewing interval itself. Therefore, the given description matches decay (fall) time.

Step-by-Step Solution:

Verification / Alternative check:

Oscilloscope measurements and component datasheets define tr (rise) = 10%→90% and tf (fall/decay) = 90%→10%, aligning with the chosen term.

Why Other Options Are Wrong:

'rise time' is for low→high transitions. 'binary level transition period' is vague and nonstandard. 'propagation delay' measures input-to-output latency, not edge slope.

Common Pitfalls:

Confusing propagation delay with slew times, or using 0–100% windows which are sensitive to noise and saturation effects.

Final Answer:

decay time