This project addresses the need for an interfacing circuit of a biosensor measurement system that operates on immobilization and hybridization process. The purpose of this project is to design a readout circuit that can capture redox reaction of electrolyte and sense small current changes in the working electrode of a 3 electrode electrochemical biosensor measurement system. The potentiostat consist of a current to voltage converter that will convert the input current into output voltage. The potentiostat is also a medium for biasing the electrodes for electrochemical technique. It also consists of several amplifiers to amplify the input that could be read by the microcontroller. This potentiostat will then be able to detect low microamperes changes in the working electrode.