ANS:D - 10% of the pulse amplitude to 90% of the pulse amplitude

In electronics, when describing a voltage or current step function, rise time refers to the time required for a signal to change from a specified low value to a specified high value. Typically, in analog electronics, these values are 10% and 90% of the step height: in control theory applications, according to Levine (1996, p. 158) , rise time is defined as "the time required for the response to rise from x% to y% of its final value", with 0%-100% rise time common for under damped second order systems, 5%-95% for critically damped and 10%-90% for over damped. [1] The output signal of a system is characterized also by fall time: both parameters depend on rise and fall times of input signal and on the characteristics of the system.