Bacteriorhodopsin is considered an important biomolecule for biochemical and technology-oriented studies. The modeling and functionality of bacteriorhodopsin sensors have been extensively studied, but the studies lack the analysis of the errors present in the measurements. Further, the impacts of these errors on photoelectric measurements are mostly unknown. In this paper, we discuss the errors caused by a transimpedance amplifier in the photocurrent measurements on a dry bacteriorhodopsin sensor. This information is especially useful when evaluating the reliability of photocurrent measurements.