关于chopper等效输入阻抗有无1/2因子的讨论

雯下蕙生香

请问为啥对于斩波的等效输入阻抗有时候会是1/fCin 而不是普遍认为的1/2fCin呢？？？

目前发现的有：
1. A Current-Mode Capacitively-Coupled Chopper Instrumentation Amplifier for Biopotential Recording With Resistive or Capacitive Electrodes
文章中说：as shown in Fig. 4(b), and Rin = 1/fchCin.

2. A Chopper Current-Feedback Instrumentation Amplifier With a 1 mHz  Noise Corner and an AC-Coupled Ripple Reduction Loop
文章中说：looking into the chopper from the integrator’s non-ideal virtual ground (node D) is given by Zsc4=1/fchC4