Fully Printed Organic Pseudo-CMOS Circuits for Sensing Applications

Fully printed organic thin film transistors (OTFTs) are promising for low-cost and light-weight flexible wearable electronics and IoT sensing nodes. To overcome process variations and enable robust designs, Pseudo-CMOS circuit style has been proposed and validated for various digital, analog and power circuits [1]. In this study, we developed a SPICE-compatible compact model for OTFT and validated the model with physical measurements. Based on the compact model, we further explored correlations between the threshold voltage (V-th) and characteristics of Pseudo-CMOS circuits. Specifically, we found that the voltage transfer curve of a Pseudo-CMOS inverter and the frequency of a Pseudo-CMOS-based ring-oscillator have linear correlations with V-th. This property can potentially be used for designing humidity, gas and sweat sensors. This design intuition has been validated with SPICE simulation and design insights are drawn from comparisons between two sensing circuitries.