Fall time explained

In electronics, fall time (pulse decay time)

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is the time taken for the amplitude of a pulse to decrease (fall) from a specified value (usually 90% of the peak value exclusive of overshoot or undershoot) to another specified value (usually 10% of the maximum value exclusive of overshoot or undershoot).

Limits on undershoot and oscillation (also known as ringing and hunting) are sometimes additionally stated when specifying fall time limits.

See also