When plotted as voltage (V) as a function of phase (θ), a square wave looks similar to the
figure to the above. The waveform repeats every 2π radians (360°), and is symmetrical about
the voltage axis (when no DC offset is present). Voltage and
current exhibiting cyclic
behavior is referred to as alternating; i.e., alternating current (AC). One full cycle is
shown
here.
The
basic
equation
for
a
square
wave
is
as
follows:
There are a number of ways in which the amplitude of a square wave is referenced, usually as
peak voltage (V
pk
or V
p
), peak-to-peak voltage (V
pp
or V
p-p
or V
pkpk
or V
pk-pk
), average
voltage (V
av
or V
avg
), and root-mean-square voltage (V
rms
). Peak
voltage and peak-to-peak
voltage are apparent by looking at the above plot. Root-mean-square and average voltage are
not so apparent.
Average Voltage (V
avg
)
As the name implies, V
avg
is calculated by taking the average of
the voltage in
an appropriately chosen interval. In the case of symmetrical waveforms like the square wave,
a quarter cycle faithfully represents all four quarter cycles of the waveform. Therefore, it is
acceptable to
choose the first quarter cycle, which goes from 0 radians (0°) through π/2
radians (90°).
As with the V
rms
formula,
a full derivation for the V
avg
formula is given here as well.
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