The amplitude of the fundamental frequency of the PWM output is thus
controlled by ma. This is significant in the case of an unregulated dc supply
voltage because the value of ma can be adjusted to compensate for
variations in the dc supply voltage, producing a constant-amplitude output.
Alternatively, ma can be varied to change the amplitude of the output. If ma is
greater than 1, the amplitude of the output increases with ma, but not linearly.