The transfer functions of the bias/detection circuits used in various laser signal njection microscopy (LSIM) techniques, especially for those using constant current bias/detection schemes, are largely unknown. This article provides both qualitative and quantitative measures of various LSIM bias/detection schemes to develop a more complete understanding of the varying measurement systems. The authors have measured the characteristics of a variety of bias/detection circuits in ways that are similar to the characterization of a linear integrated circuit. They have concentrated on examining the frequency response, pulse response, and noise levels. It was found that the LSIM bias/detection systems have widely varying characteristics which, in turn will affect how they can be optimized. Furthermore, the relationship between the frequency and noise characteristics of the bias/detection systems and the input signal that is to be detected point to differing ways in which the systems can be modified for improved performance.