Development of procedures and evaluation strategies for novel field-effect transistor sensors

Abstract

In order to evaluate new types of sensors based on the field-effect transistor technology, a cost-effective measurement and control system is developed. Because some new types of transistor-based sensors are particularly prone to drift and noise, a measurement system is built around evaluating the effect of a biasing technique known as switched biasing, which has been shown to reduce drift under certain configurations. The result is an implementation of software and hardware that is both able to control a transistor with switched biasing, explore drift-reducing switched biasing configurations, and accurately measure its performance with relatively high precision. Pre-Filtering of the measured data coupled with a fast actuation of an analog-to-digital converter is realized and implemented on a FPGA in the form of a rate-adjustable CIC decimation filter, which increases the signal-to-noise ratio and reduces the required data-transfer rate. The measurement system is controlled internally by a microcontroller and is interfaced through a USB interfaces to a higher-level system, such as a computer running MATLAB, and allows for multiple measurement systems to be operated in parallel. Systematic errors related to limitations of measurement hardware such as offset, temperature and drift are evaluated and compensated for through calibration.