A Threshold-Voltage Compensation Circuit for Organic Thin-Film Transistor Active-Matrix Neurostimulation System

Organic thin-film transistor (OTFT) is a promising device technology for flexible large-area high-channel-count active-matrix neurostimulation system due to its flexibility and biocompatibility. However, circuits made by OTFT might be sensitive to device variation. As a result, it is difficult to achieve precise neurostimulation without any compensation structure in the pixel circuits. This work proposes a 6T2C threshold voltage compensation circuit for neurostimulation, which has low output current variation of 10.53%, reduced from the variation of 17.85% without compensation. We also improve the OTFT fabrication process with encapsulation to allow the circuits to operate under an electrolyte environment. Using the pixel circuits, we implement a 256-channel active-matrix neurostimulation system. The system can output stimulation with any pattern and allow each channel to output independently and simultaneously.