An EGFET Based Common Source Amplifier as a Low-Frequency Instrumentation Amplifier for Sensitivity Measurement on RuO2 Lactic Acid Biosensor

In this study, a low-frequency instrumentation amplifier (LFIA) integrated with an extended-gate field-effect transistor (EGFET) is presented to realize the simplicity common source amplifier (CSA) structure. The proposed EGFET CSA was developed by the 0.18-
$\mu \text{m}$
CMOS process technology of Taiwan Semiconductor Manufacturing Company (TSMC). The EGFET CSA has low frequency and noise immunity function, and it can effectively output the response signal, with good stability and effectively improve the sensitivity, not susceptible to environmental factors, easy to replace, and low cost. Moreover, the simple circuit design of the EGFET CSA was used to analyze the sensing characteristics and to improve the stability of the ruthenium dioxide (RuO
₂
) lactic acid (LA) biosensor. Therefore, the EGFET CSA is suitable for LA detection. The simple process of the EGFET CSA was used to analyze the sensing characteristics and to improve the stability of the ruthenium dioxide (RuO
₂
) lactic acid (LA) biosensor. An arrayed potentiometric LA biosensor based on the RuO
₂
thin film was proposed and manufactured in this study. The experimental results indicated that the EGFET CSA as a low-frequency instrumentation amplifier has achieved a good sensitivity (53.41mV/mM) and satisfactory linearity (0.997) on the RuO
₂
LA biosensor as compared with the V-T measurement system.