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设计了一款用于MEMS麦克风的模数转换接口电路。该电路包含一个前置放大器和一个四阶Delta-Sigma调制器。前置放大器包括一个pMOS输入的源级跟随器和一个仪表放大器。放大器设计中采用了斩波稳定技术消除低频闪烁噪声。Delta-Sigma调制器采用了带有前馈支路的四阶结构,其优点在于低积分器摆幅,可以降低积分器中放大器的非线性增益对电路性能的影响。该电路采用0.18μm CMOS工艺制作,电源电压为1.65μV。测试结果表明,电路可以达到80 dB的动态范围和73.4 dB的峰值信号对噪声加谐波比。电路的耗散电流为1 500μA,占用的芯片面积为0.48 mm2。
A analog to digital conversion interface circuit for MEMS microphones was designed. This circuit includes a preamplifier and a fourth-order Delta-Sigma modulator. The preamplifier includes a pMOS input source follower and an instrumentation amplifier. Amplifier design uses chopper stabilization technology to eliminate low-frequency flicker noise. The Delta-Sigma modulator uses a fourth-order architecture with a feedforward branch, which has the advantage of low integrator swing, which reduces the effect of the amplifier’s nonlinear gain on the circuit’s performance. The circuit is fabricated in 0.18μm CMOS technology with a supply voltage of 1.65μV. Test results show that the circuit can achieve dynamic range of 80 dB and 73.4 dB peak signal to noise plus harmonic ratio. The circuit dissipates a current of 1,500 μA and occupies a chip area of 0.48 mm2.