Conventional Hi-Fi audio amplifiers could not have used global feedback except some local feedbacks for high-fidelity due to time delay of feedback loop and so have been designed using class-A amplifier with the highest fidelity of analog ones in spite of the lowest efficiency. Therefore, they have a restrictive ability of repressing the distortion and show considerably poor power efficiency.
This thesis presents a mixed-mode amplifier with high-fidelity and high-efficiency, which is composed of two analog amplifiers. In other words, the one is a class-A amplifier with high-fidelity as a master and the other is a class-B amplifier with high-efficiency as a booster. In addition to this new structure, a useful design technique is proposed to enhance the linear range at the input stage.
Experimental results show that the new analog-analog mixed-mode amplifier attains about 64.1% power efficiency at 250W output power and the minimum 0.03% Total Harmonic Distortion(THD).
