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A 1215-dB THD Class-D Audio Amplifier With 49-dB LC Filter Nonlinearity Suppress
提出一种双环路架构的D类音频放大器，抑制LC滤波器非线性49dB，THD达-121.5dB。
180-nm BCD, -121.5-dB THD, -107.1-dB THD+N, 21W@4Ω, 12W@8Ω
D类放大器LC滤波器非线性抑制双环路架构音频放大器
▸创新点1：双环路架构（系统创新） - 采用内环和外环的双环路设计，内环确保系统稳定性，外环提供高增益以有效抑制LC滤波器和输出级的非线性，实现了-121.5dB THD的高性能指标。
▸创新点2：LC滤波器非线性抑制（方法创新） - 通过外环高增益设计，显著抑制LC滤波器的非线性失真，达到49dB的抑制效果，大幅提升了音频信号的保真度。
▸创新点3：鲁棒性设计（电路创新） - 在LC滤波器截止频率变化±30%（62kHz至106kHz）的情况下，THD性能波动不超过3dB，展现了极强的环境适应性和稳定性。
▸创新点4：高效率输出（性能创新） - 在4Ω负载下实现21W输出功率（87%效率），8Ω负载下实现12W输出功率（91%效率），兼顾了高功率输出与能源效率的平衡。
Abstract
Class-D audio amplifiers produce electromagnetic
interference (EMI), which often needs to be suppressed by an
external LC filter. However, due to component nonlinearity, this
filter can itself cause significant distortion. This article presents a
class-D amplifier that suppresses LC filter nonlinearity by 49 dB
and is robust to ±30% variations in its cutoff frequency. This
is achieved by a dual-loop architecture, in which an inner loop
provides stability, while an outer loop provides the high gain
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