Electronic Engineering Dictionary

Digital Pulse Terms:

Pulse. A signal characterized by a steep rise from and decay toward an initial level.

Pulse Shape

Pulse Amplitude. The magnitude of a pulse parameter, such as the field intensity, voltage level, current level, or power level. Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as average, instantaneous, peak, or root-mean-square.

Pulse Average Time. The time duration from a point on the leading edge which is 50 percent of the maximum amplitude to a point on the trailing edge which is 50 percent of the maximum amplitude [tW1 or tW2 in the diagram below].

Pulse Delay Time. The time interval from a point at which the leading edge of the input pulse has risen to 10 percent of its maximum amplitude to a point at which the leading edge of the output pulse has risen to 10 percent of its maximum amplitude [Pd in the diagram below].

Pulse Droop. Also called Voltage Droop. The reduction in output level, over time, caused by driving a load. Detailed Voltage Droop Definition. The slow decay or reduction in voltage of the level of a voltage pulse.

Pulse Duration. [PD] The period of time during which a pulse is present, measured at the 50 percent point. In a pulse waveform, the interval between (a) the time, during the first transition, that the pulse amplitude reaches a specified fraction (level) of its final amplitude, and (b) the time the pulse amplitude drops, on the last transition, to the same level. Note: The interval between the 50% points of the final amplitude is usually used to determine or define pulse duration, and this is understood to be the case unless otherwise specified. Other fractions of the final amplitude, e.g., 90% or 1/e (where e = 2.71828. . .), may also be used, as may the root-mean-square (rms) value of the pulse amplitude.

Pulse Fall Time. The period of time during which a pulse falls from ninety percent of its initial high value to ten percent of its final value, or steady state value. Fall Time Graph. [Tf in the diagram below].

Pulse Jitter. Time jitter is determined by examining an O-scope presentation of a voltage or current pulse and is measured at 50 percent of the pulse amplitude. Pulse jitter or time jitter may also be measured with respect to the trigger pulse or some other reference. Refer to the general Definition of Signal Jitter. Also see the Jitter Measurement graphic to the right.

Pulse Oscillations. Another term for pulse ringing, although ringing normally damps out over time while an oscillation may not. An oscillation riding on a pulse may appear the same as pulse ripple, although the frequency of oscillation may determine the cause.

Pulse Overshoot. The amount of voltage rise above the steady state value. Overshoot occurs on the initial rise of the signal pulse.

Pulse Rate. The time interval between the start of one pulse and the beginning of the next pulse, measured at the same voltage level for both pulses. Also called Pulse-Repetition Rate [PRT], Pulse Rep Rate. Also see Pulse-Repetition Frequency [PRF].

Pulse Ringing. A damped oscillation that occurs at each edge of a pulse. Also refer to the Definition of Damped Wave. Pulse ringing causes a positive overshoot [the maximum positive voltage] and a positive undershoot; in addition to a negative overshoot [the maximum negative voltage] and a negative undershoot. Pulse ringing differs from pulse ripple in that the signal is damped and not a constant amplitude.

Pulse Ripple. The application of an varying AC voltage [normally a sine wave] to a pulse. Read more on the Definition of Ripple Voltage. Also see Pulse Oscillation.

Pulse Rise Time. The period of time during which a pulse rises from ten percent of its initial value to 90 percent of its final value, or steady state value. Rise Time Graph. [Tr in the diagram below].

Pulse Spike. A short duration large change in pulse amplitude, greater than either ripple or over-shoot voltage and lasting less than 10 percent of the pulse width.

Pulse Storage Time. The time interval from a point 10 percent down from the maximum amplitude on the trailing edge of the input pulse to a point 10 percent down from the maximum amplitude on the trailing edge of the output pulse. [Ts in the diagram below].

Pulse Time. The time interval from the point on the leading edge which is 90 percent of the maximum amplitude, to the point on the trailing edge which is 90 percent of the maximum amplitude. [Tp in the diagram below].

Pulse Undershoot. The amount of voltage rise "fall" below the steady state value. Under-shoot occurs on the final fall of the signal pulse.

Pulse Width. Duration of time between the leading and trailing edges of a pulse.

Pulse Width Duration. See Pulse Duration.

Pulse Characteristics

Design note; not all cases will result in an output waveform that just gets delayed in time from the input waveform. The test circuit below is a schematic to test the pulse response of a 2N718A transistor. Note the difference between the input waveform and the expected output signal.

2N718 Pulse Response Test Circuit