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介绍了数字电话系统中用户线接口电路的一个重要电路——基于数字信号处理（ＤＳＰ）和ΣΔ调制技术的新一代编解码器（Ｃｏｄｅｃ）。设计了一种带二阶ΣΔ调制器和ＣＭＯＳ能隙基准电压源的四信道Ｃｏｄｅｃ模拟前端，分析了其中关键的过采样ΣΔ调制Ａ／Ｄ转换技术的基本原理。电路采用１．２μｍＣＭＯＳ双层多晶双层铝工艺实现，并利用信号处理数学软件ＭＡＴＬＡＢ和晶体管级电路模拟工具ＨＳＰＩＣＥ完成电路的模拟和验证。单信道模拟前端５Ｖ电源工作，功耗２５ｍＷ，芯片面积约３ｍｍ２。
An important circuit of the subscriber line interface circuit in digital telephone systems is introduced - a new generation of codec based on digital signal processing (DSP) and ΣΔ modulation technology. A four-channel Codec analog front end with a second-order ΣΔ modulator and a CMOS bandgap voltage reference is designed, and the basic principle of the key oversampling ΣΔ-modulated A / D conversion technique is analyzed. The circuit adopts 1.2μmCMOS double-layer polycrystalline double-layer aluminum technology to achieve, and the use of signal processing software MATLAB and transistor-level circuit simulation tool HSPICE circuit simulation and verification. Single-channel analog front-end 5V power supply, power consumption 25mW, chip area of about 3mm2.