Three-stage ring oscillator with organic transistors

The paper aims to address the issues of circuit integration of organic thin film transistors (OTFT) into a ring oscillator module. The stress falls on the optimization of the connections of the inverters in each of the stages of the presented three-stage ring oscillators. The organic transistors, with Bottom Contact Top Gate architecture, are fabricated using commercially available materials and accessible deposition techniques, such as spin-coating and metal evaporation. Two ring oscillators are fabricated with manual and patterned interconnections. The first circuit has a widthlength ratio of 1:10 between the load and drive transistors, while the second structure has a 1:30 ratio. The current-voltage measurements on the individual transistors, as well as the electrical measurements onto inverters and onto the whole circuit, are performed with a Keithley 4200 Semiconductor Analyzer. All measurements are done in accordance with the 1620.1 standard, in air and under normal ceiling fluorescent light illumination. The stability of the individual devices and the overall circuit is proved to remain constant under normal working conditions.