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A Low-EMI 3-W Audio Class-D Ampli fier Compatible With AM/FM Radio
一款兼容AM/FM收音机的低EMI 3W音频D类放大器，采用驱动斜率控制和数字调制技术。
2.7-6.6V, 95dB SNR, 85%效率
D类放大器电磁干扰AM/FM兼容H桥线性化电源抑制比
▸驱动斜率控制降低FM频段EMI
▸数字调制在AM频道形成零陷
▸两种反馈技术线性化H桥并提升电源抑制比
Abstract
A 3-W audio class-D ampli fier compatible with AM/FM radio while requiring minimal external filtering is pre- sented. The ampli fier uses driver slew rate control to reduce electromagnetic interference (EMI) in the FM band and dig- ital modulation to spread the PWM common-mode signal and place a null at the tuned AM channel. Two original feedback techniques are employed to linearize the H-bridge. One cancels signal-dependent pr opagation delays in the H-bridge to improve harmonic distortion and elimina te high-frequency noise folding into the audio band. The second technique boosts the power supply rejection ratio to simplify and reduce the cost of supply filters. The ampli fier system, implemented in a standard 110-nm CMO S process, operates with a supply voltage ranging from 2.7 to 6.6 V and achieves an SNR of 95 dB and 85% ef ficiency.