Projeto de potenciostato com espelho de corrente CMOS aplicado a uma célula eletroquímica de três eletrodos

Abstract

Electronic devices for electronic instrumentation and analytical chemistry research applications are of great interest due to their wide applicability, both in applied research and in the industrial environment. These devices, which are composed of highly sensitive and selective electrochemical sensors, enable accurate analyses in the detection of various chemical and biological compounds, such as oxygen, glucose, metals that are toxic to the environment, as well as antioxidant and biochemical molecules and DNA. Such applications are particularly relevant for environmental monitoring and biomedical areas. The electrochemical techniques employed in these sensors present significant advantages compared to other detection methods, such as high sensitivity, good selectivity, wide applicability and low cost in the development and physical implementation of the device. In this context, this work presents a new compact circuit designed for a CMOS potentiostat, applied to a three-electrode electrochemical cell. The proposed topology acts as a circuit interface, controlling the polarization of voltage signals on the sensor electrodes, in addition to facilitating the measurement of current during the oxidation-reduction process of the analyzed solution. The potentiostat was developed using CMOS technology and consists of a two-stage amplifier, two current mirror blocks coupled to the amplifier, and a CMOS pushpull inverter output stage. The electrochemical cyclic voltammetry method was employed, operating in a voltage range of ±0.8 V and scan rates of 10 mV/s, 25 mV/s, 100 mV/s, and 250 mV/s. The circuit is capable of measuring currents ranging from 10 μA to 500 μA. The experimental results were obtained using a redox solution of potassium ferricyanide K3[Fe(CN)6] with concentrations of 10, 15, and 20 mmol/L, whose corresponding voltammograms were evaluated. The results demonstrated that the topology of the proposed potentiostat presents performance consistent with commercial equipment. Furthermore, its implementation with discrete components manufactured using CMOS technology processes allows integration into more compact and efficient systems, reducing both the size and cost of electrochemical devices, without compromising the accuracy and reliability of analyses.