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States the way of improving the efficiency of audio frequency amplifer and introduces circuit of D-type amplifer . It also introduces full wave bridges bipolar output circuit and full utilize may melody high and low proportion of PWM sigal to improve great range efficiency .

论述了提高音频放大器效率的方法，介绍了D类放大器的电路组成，输出采用全桥式双极输出，采用占空比在0-100%可调的PWM信号进行控制使效率得到大幅度的提高。