In a switching amplifier for generating a pair of output signals of square
waves in response to an input signal, when the input signal is zero, the
first output signal has a first duty cycle and the second output signal
has a second duty cycle; when the input signal is greater than zero, the
first output signal has a third duty cycle varying with the input signal
and the second output signal still has the second duty cycle; and when
the input signal is less than zero, the first output signal has the first
duty cycle and the second output signal has a fourth duty cycle varying
with the input signal. The first and second duty cycles are very small
but equal to each other in size, and the phase difference between the
first and second output signals could range from 0 to 180 degrees.