A switching amplifier includes a level shifting circuit for adjusting a voltage level of an original input signal to generate a first input signal and a second input signal. The first input signal is identical to the original input signal except for referring to a first reference level. The second input signal is identical to the original input signal except for referring to a second reference level. In response to the first input signal and an oscillating signal, a first control circuit generates a first width-limited PWM signal for controlling a first half-bridge switching circuit. In response to the second input signal and the oscillating signal, a second control circuit generates a second width-limited PWM signal for controlling a second half-bridge switching circuit.