Input-output Transfer Function Analysis of a Photometer Circuit Based on an Operational Amplifier

Abstract

In this paper an input-output transfer function analysis based on the frequency response of a photometer circuit based on operational amplifier (op amp) is carried out. Op amps are universally used in monitoring photodetectors and there are a variety of amplifier connections for this purpose. However, the electronic circuits that are usually used to carry out the signal treatment in photometer circuits introduce some limitations in the performance of the photometers that influence the selection of the op amps and other electronic devices. For example, the bandwidth, slew-rate, noise, input impedance and gain, among other characteristics of the op amp, are often the performance limiting factors of photometer circuits. For this reason, in this paper a comparative analysis between two photodiode amplifier circuits is carried out. One circuit is based on a conventional current-to-voltage converter connection and the other circuit is based on a robust current-to-voltage converter connection. The results are satisfactory and show that the photodiode amplifier performance can be improved by using robust control techniques.