b. Reference periods. In many RC and RL circuits, the response
of a circuit to a waveform depends on the relationship of the time
constant (TC) of the circuit to the reference periods of the
waveform. The rise, duration, and decay times are the reference
periods of a pulse. The reference periods of two waveforms are shown
in Figure 16.
Figure 16. Pulse reference periods
(1) Period. The period (P) of any waveform is the time
required to completed one full cycle of operation. The period of a
waveform has the same meaning as the pulse repetition period (PRP).
The formula for the period of a waveform is the same as the formula
used in determining the PRP. (Frequency is given in pulses per
second or hertz.)
PRP (seconds) = 1/PRF
PRP (microseconds) = 106/PRF
Period (seconds) = 1/Frequency
(2) Rise. A pulse's rise time (tr) is the time required for
the pulse to rise from zero to maximum. In practical use, a pulse's
rise time is the time required for the pulse to rise from 10 percent
to 90 percent of its maximum value.