Enhancing the Measurement Sensitivity and Repeatability of Electrolyte-Insulator-Semiconductor Capacitor Sensor With Impedance Conversion

The measured performance of the electrolyte-insulator-semiconductor capacitor (EISCAP) is related not only to the device structure and technology, but also to the measurement methods. For the conventional amplitude measurement method, since the capacitance of EISCAP is very small, the measurement procedure is easily affected by the fluctuation of the reference electrode and solution impedance, which leads to low sensitivity and poor repeatability. In this study, a measurement method with impedance conversion is proposed for enhancing the measured sensitivity and repeatability of the EISCAP. Different from the conventional measurement method, an impedance conversion stage is inserted in front of the transimpedance amplifier in this approach; thus, the fluctuation of the impedance of the solution and reference electrode is suppressed, and the measurement repeatability is improved. At the same time, the capacitance of the sensor has been significantly amplified, so that the sensitivity can be improved. Under the condition of 2 kHz, compared with the traditional measurement method, the measurement sensitivity and repeatability with the proposed approach were improved by 13.81% and 63.64%, respectively.