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要满足采样两个信号差的需求,有两种经典的方案。一种方案是用一个仪表放大器将两个输入信号相减,仪表放大器的输出再连接到一个经典采样保持放大器的一只输入端。对一个单增益差分仪表放大器,优点是无需外接电阻,但这种方案也有不足,当输入极性相同,幅度相近时,它有相对较高的输出失真。此时,两个输入信号的差值接近于0V,因此放大器更容易受采样与保持放大器残余动态缺陷的影响。
To meet the needs of sampling two signals, there are two classic solutions. One solution is to subtract the two inputs with an in-amp and the output of the in-amp to an input of a classical sample-and-hold amplifier. The advantage of a single-gain differential instrumentation amplifier is that no external resistors are required, but this solution is not sufficient. It has a relatively high output distortion when the input polarities are the same and the amplitudes are similar. At this point, the difference between the two input signals is close to 0V, so the amplifier is more susceptible to residual dynamic defects in the sample and hold amplifier.