ISFET drawbacks minimization using a novel electronic compensation

Ion sensitive field effect transistor (ISFET) and membrane field effect transistor (MEMFET) have some drawbacks related to: long-term drift, hysteresis and thermal drift. These factors limit the accuracy of ISFET/MEMFET based measurements systems, specially for continuous or long period measurements. Due to its accuracy, repeatability and easy-to-use features, electronic instrumentation systems are the best tools to design ISFET/MEMFET based measurement systems. A well-designed hardware and a qualified virtual instrumentation software are the key factors to overcome and compensate hysteresis, thermal and long-term drifts ISFET/MEMFET limitations. The paper is dedicated to show an instrumentation system designed to compensate long-term drift on ISFET/MEMFETs. First, this limitation is experimentally shown. As a consequence of it, an electronic hardware is designed to supply correct sensor voltage and current bias levels. On the other hand, an acquisition and control algorithm is implemented. The software acts over the hardware selecting appropriate voltage bias levels compensating sensor drifts. Experimental results demonstrate the effectiveness and feasibility of the instrumentation system proposed.