| In the audio power amplifier market, the class AB has been in a dominant position. In recent years, with mp3,DVD,mobile phones and other portable consumer electronic products is becoming popular, Class-D audio power amplifier is being widely used with the advantages of high efficiency and small size. It is therefore of great importance to study it.A Class-D amplifier with conventional PWM modulation not only has large static power consumption, but also requires an output filter which needs large area and increasing cost. Therefore, A filterless Class-D audio amplifier is implemented in this paper. The following technologies are taken in the implementation: a new modulation scheme is used to minimize static power consumption of the system; chopper technique is adopted in preamplifier to reduce input noise and offset; feedback is applied to reduce the total harmonic distortion.The chip is designed in CSMC 0.5um Bicmos process. The core die size is 0.79*0.83mm2.The entire circuit contains a preamplifier,an error amplifier,two comparators,oscillator,gate-driver circuit,full-bridge,reference circuit,over-temperature protection circuit and over-current protection circuit. The designed Class D audio power amplifier can deliver 1.4W output power to an 8 ohm load when THD is less than 10% and achieves a power efficiency of 86% when it delivers 1.25W to an 8 ohm load. |
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