Abstract: A dual mode power amplifier for an audio signal operates in linear mode at lower levels of the audio signal and in switched mode (Class D) at higher levels of the audio signal.

Abstract: A PWM generator (100; 200; 300; 400) is described, which does not require a separate saw-tooth generator and a separator for generating a modulated pulsed signal. According to the invention, the input signal (Sin) is supplied to one input terminal (111) of a comparator (110), which receives at its other terminal (112) a feedback signal which is derived from the output signal (Sout) via an integrator device (150), in such a way that the circuit is self-oscillating. The feedback signal is a sloping signal. The comparator switches its output when the feedback signal crosses the level of the input signal, which in turn causes the feedback signal to invert its slope. Thus, the feedback signal in effect provides a saw-tooth signal without being generated by a separate saw-tooth generator.