Comparative study of CMOS lock-in amplifiers for wideband bioelectrical impedance measurements

摘要

In this paper, limitations of two-phases lock-in amplifiers (LIAs) in variable frequency applications are reported. Given those limitations, an alternative LIA architecture is described: the heterodyne LIA. Design strategies for improving general performance of heterodyne LIA without sacrificing power consumption have been described. Comparative simulations of both architectures have been carried out with MATLAB Simulink. Heterodyne LIA architecture permits measuring signals in a wide range of frequencies with higher improvement in signal-to-noise ratio and simpler design than the conventional two-phases LIA architecture.