A switching power amplifier of class D has a switching stage for
generating a block wave signal by alternately switching the block wave
signal between supply voltages. A filter (24, 25) generates a power
output signal (22) corresponding to an input signal to be amplified,
which is coupled to a linear input (19) that is free of hysteresis. A
control circuit (27, 28, 29) provides feedback between the output power
signal and the linear input for controlling both the gain in the
operational frequency range and also the alternately switching of the
switching stage. Hence, the amplifier oscillates controlled via the same
feedback loop that also controls the operational behavior of the
amplifier, resulting in low output impedance and low distortion.