Multi-channel audio power amplifier

A power amplifier for amplifying audio frequency signals that may have frequency components within a first range of frequencies, comprising:

• a driver amplifier for amplifying an input signal, the driver amplifier being operable over the entire first range of frequencies,
• a high frequency analog power amplifying circuit having an input coupled to the driver amplifier for power-amplifying with a substantially flat gain components of an output signal from the driver amplifier that are within a second range of frequencies within the first range;
• a low frequency pulse modulation and demodulation circuit having an input coupled to the driver amplifier for power-amplifying components of an output signal from the driver that are within a third range of frequencies within the first range, the first range including at least one frequency that is lower than any frequency in the second range, the pulse modulation and demodulation circuit comprising a pulse width modulator operating at a predetermined carrier frequency and an inductor coil acting as a low pass filter having a cut-off frequency lower than that of the carrier;
• an output terminal for delivering an output signal of the power amplifier including signals from both the high frequency analog amplifier and the low frequency pulse circuit;
• a resistor having an impedance higher than that of the low pass filter of the pulse modulation and demodulating circuit for frequencies in the third range coupling an output of the high frequency analog power amplifying circuit to the output terminal;
• and
• a negative feedback circuit providing a negative feedback from the output terminal to the driver amplifier.