Substantial improvement in solution-processed organic thin film transistor (OTFT) technology has shown the possibility of their potential deployment in radio-frequency identification tags, the back-plane circuit of flexible displays, sensors, and biodegradable circuits due to having inexpensive low-temperature processing along with mechanical flexibility. A systematic methodology to build up circuit design, incorporating the device characteristics is highly desirable for establishing a self-consistent design rule. In the present work, OTFTs, consisting of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) as semiconductor and cross-linked poly(4-vinylphenol) (c-PVP) as gate dielectric are fabricated on both rigid glass substrate and flexible polyethylene terephthalate (PET) substrate. The electrical characteristics of fabricated OTFTs are used for circuit design and simulation using the LTspice simulator. The computer-aided design (CAD) layout of a three-layered photomask for the inverter and ring oscillator circuits is designed and fabricated in our lab. Two varieties of photomask are used, resulting in different fabrication process flows. The first process flow creates interconnections near the edge wiping region. In the second process flow, interconnects are formed using vias. The fabricated circuits are characterized and are found to be consistent with the simulation.