A Temperature Compensation Circuit Applied to Extended Gate Field Effect Transistor Based on the RuO2 Ascorbic Acid Sensing Window

This article presents an extended gate field-effect transistor (EGFET) biosensor for sensing ruthenium dioxide (RuO 2 ) ascorbic acid. The device was modified by the addition of a temperature compensation circuit. The proposed circuit was simulated, fabricated, and tested using a TSMC 180-nm CMOS process. When the temperature ranged from 25~^{\circ }\text{C} to 60~^{\circ }\text{C} , V_{\mathrm {out}} presented very little drift as temperature increased. The temperature coefficient (TC) had positive and negative sections, with a value of 0.348 mV/°C and 0.17 mV/°C, respectively. The difference between the maximum output voltage and the minimum output voltage was 8.7 mV when the temperature was at 25~^{\circ }\text{C} - 60~^{\circ }\text{C} . When the ascorbic acid concentration ranged from 0.0078 to 2 mM, the RuO 2 ascorbic acid sensing window exhibited impressive voltage sensitivity of 54.52 mV/decade and linearity of 0.996. A voltage-time (V-T) measurement system was used to verify the sensing characteristics of the device which had a high average sensitivity of 58.43 mV/decade and good linearity of 0.995. The device had a fast response time of 17 s and a low limit of detection (LOD) at 1.5~\mu \text{M} . The selectivity of this enzymatic RuO 2 sensing window to ascorbic acid was high when compared to other interfering substances that may be found in the human body.