Analysis and Measurements of an Urea Biosensor Based on Instrumentation Amplifier Chip With Cross-Coupled Technique

In this work, we design a high common-mode rejection ratio (CMRR) and low unity gain frequency (UGF) cross-coupled instrumentation amplifier (CCIA). This design was implemented by the Taiwan Semiconductor Manufacturing Company (TSMC) 0.18- $\mu \text{m}$ CMOS process technology. By using the three proposed cross-coupled operational amplifier, the CCIAs was designed with the power supply of +1.8 and −1.8 V. The instrumentation amplifier (IA) achieved a voltage gain of 56.92 dB with a CMRR of 126.08 dB. This IA was applied on an arrayed RuO2 urea biosensor as a readout circuit. Moreover, the sensing characteristics of the urea biosensor were analyzed. The experimental results show that our arrayed RuO2 urea biosensor combined with CCIA has a good average sensitivity of 2.933 mV/(mg/dL) and a linearity of 0.998. With the proposed IA, an effective measurement system can be achieved due to simplicity, convenience, and low cost.