D類音頻放大器高效率的優點使其為目前常見的音頻放大器之一，但其常用脈寬調變方式，在差共模輸出均具有快速切換之訊號，使在30M至1GHz的頻帶上產生不可忽視的差共模電磁干擾。本論文功率級採用無共模BD調變，並提出一輸出共模校正技術，降低採用該調變之輸出級切換時產生之共模訊號抖動，進而提高其共模干擾降低效果。此外為解決D類放大器高失真的缺點，此晶片除使用閉迴路架構外，也採用一前饋式脈寬調變互調失真抑制技術，改善閉迴路本身具有的脈寬調變互調失真，達成低總失真加雜訊的目標。
本論文晶片實現於0.5微米互補金屬氧化物半導體技術，經驗證後，其結果顯示在5伏特之電源電壓，8歐姆之揚聲器負載可達到最低-99.6dB之總諧波失真加雜訊。另外，相對一般CMFBD功率級，此晶片之技術預計可額外增加11dB之共模電磁干擾降低效果。

Class-D is one of the commonly used amplifiers in recent year for its high efficiency. However, with conventional BD modulation, its rapid-switching output radiates serious differential and common-mode electromagnetic interference (EMI) in the frequency range of 30M~ 1GHz. This work adopts the Common-Mode Free BD (CMFBD) modulation in the low-EMI power stage, and an output common-mode correction is proposed to further improve common-mode EMI suppression by reducing common-mode spikes during power stage switching. To achieve low THD+N, this work not only uses closed-loop structure to reduce the distortions of class-D power stage, but also adopts the Feed-Forward PWM Intermodulation Distortion Reduction (FFPIDR) to reduce PWM intermodulation distortion from closed-loop structure.
Implemented in 0.5μm CMOS technology, this work reaches minimum -99.6dB THD+N after circuit verification under 5V supply, on an 8-Ω load. On the other hand, compared with other CMFBD state of the arts, the proposed output common-mode correction is expected to further increase 11dB common-mode EMI reduction.

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