Audio amplifier

An audio amplifier comprising:

• a power amplifier circuit for amplifying an audio signal;
• a power supply for supplying a direct current to the amplifier circuit;
• the power amplifier circuit having an output stage for coupling the amplifier to an audio transducer,
• the power supply coupled to and responsive to the output stage for reducing the voltage available to the amplifier in response to power drawn:
• first and second output stages disposed in staggered relationship,
• means for coupling the power supply to the first output stage;
• means for adjusting the voltage rails available from the power supply, the voltage rails adjustment means coupled to and responsive to the output stage and coupled to the power supply;
• the first output stage comprising means for operating at a first duty cycle with a first duty factor, the second output stage comprising means for operating at a second duty cycle with a second duty factor, the second duty factor greater than the first duty factor, and the second duty cycle shorter than the first duty cycle,
• whereby the voltage rails required to drive the output stage is limited by the extent of output so that a significant audio output signal is available, despite minimal size.

An audio amplifier comprising:

• an input stage for receiving an audio signal;
• an output stage for coupling an amplified audio signal to an audio transducer;
• the output stage having a plurality of staggered intermediate stages, including a first stage comprising first amplifying means for operating over a first duty cycle at a first duty factor, and a second stage comprising second amplifying means for operating over a second duty cycle at a second duty factor, the second duty factor being in excess of the first duty factor,
• whereby the first duty cycle is greater than the second duty cycle, thereby allowing the use of more economical, yet responsive higher quality semiconductor components at the first stage, without the necessity for protection circuitry.