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过采样和噪声整形中的∑-△调制是高精度A/D变换器中使用的一种著名技术。通信应用就使用这样的变换器,它的特性是由交流性能(如信噪比)来表征的,而且主要是用于允许有失调和增益误差的场合。另一方面,在测量和仪表应用中却要求绝对精度,例如不允许有失调误差和增益误差。这些应用是通过直流特性,如微分和积分线性误差、失调和增益误差等,来表征的,常常要求很高的分辨率。二级增量A/D变换器就可满足这样的要求,这种变换器使用了简单的数字滤波器中的∑-△调制技术。作者通过采用SACMOS 3μm技术制作的电路进行了实验,结果表明,即使用低的参考电压也完全可以获得15位的绝对精度。
Sigma-Delta modulation in oversampling and noise shaping is a well-known technique used in high-precision A / D converters. Communication applications use inverters whose characteristics are characterized by ac performance (such as signal-to-noise ratio) and are primarily used to allow for offsets and gain errors. On the other hand, absolute accuracy is required in measurement and instrumentation applications, for example, offset and gain errors are not tolerated. These applications are characterized by DC characteristics such as differential and integral linearity errors, offset and gain errors, and often require high resolution. This is met by a two-stage incremental A / D converter that uses a simple delta-sigma modulation technique in a digital filter. The authors conducted experiments with a circuit fabricated using SACMOS 3μm technology and found that 15-bit absolute accuracy was fully achieved even with low reference voltages.