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In this brief, the performance analysis of a photometer circuit based on a robust two degrees-of-freedom controller is presented. Here, the closed-loop transfer function of the complex feedback system is shown as a function of the operational amplifier parameters. Also, the stability region of the robust photometer circuit is calculated, and the performance of this circuit is compared against the performance of a photometer circuit based on a basic current-to-voltage converter connection. Both the simulation and experimental results are satisfactory and show the importance of applying robust control techniques to the design of photometer circuits.