![]() ![]() Since then, field effect transistor (FET) based electrochemical sensors 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 have been extensively investigated due to their enhanced sensitivity, resolution, low power, portability and fabrication compatibility with silicon processing technology. The application of field effect transistors (FET) as transducers in electrochemical sensors was first described in 1970 by Bergveld 1. In summary, the BJT device is demonstrated to be a superior transducer in comparison to a FET in an electrochemical sensor. As a demonstration for mobile applications, these BJT sensors are further investigated by measuring chloride levels in artificial human sweat for potential cystic fibrosis diagnostic use. Hence, a BJT sensor can make quantitative sensing measurements with minimal calibration requirements, an important characteristic for mobile sensing applications. Unlike a FET sensor, the calibration curve of the BJT sensor is independent of applied voltages. Also, sensor calibration curves are impacted by the transducer choice. Sensitivity is also enhanced: BJT sensing signal changes by 10 times per pCl, whereas the FET signal changes by 8 or less times. Signal to noise ratio is 20 to 2 times greater for the BJT sensor. Comparative measurements show that the transducer choice significantly impacts the electrochemical sensor characteristics. Measurements are performed on two chloride electrochemical sensors that are identical in all details except for the transducer device type. In this report, a FET transducer is compared with the recently proposed bipolar junction transistor (BJT) transducer. Field effect transistors (FET) have been widely used as transducers in electrochemical sensors for over 40 years. ![]()
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