An all-vacuum evaporated approach to the roll-to-roll (R2R) fabrication of organic electronic circuits is being developed for potential applications in, for example, display backplanes and integrated security tagging for packaging. As part of an on-going development process, we are now addressing the question of circuit design and simulation. Here we describe the first step in this process, namely the extraction of parameters from experimentally-obtained output and transfer characteristics of vacuum produced, thin film transistors based on the organic semiconductors pentacene and dinaphtho[2,3-b:2$'$3 $'$-f]thieno[3,2-b]thiophene (DNTT). For this we use Silvaco's Universal Thin Film Transistor (UOTFT) Model $({rm Level}=37)$ so that the extracted parameters may be used directly with Silvaco's Gateway circuit simulation software.