Organic thin-film transistors (OTFTs) are an emerging technology for large scale circuit integration, owing the availability of both p-and n-channel devices. For the technology development and the design of circuits and digital systems, the accurate physical modeling is mandatory. In this work we propose an unified analytical model for both p-and n-type OTFTs. The model is physically based and accounts for a double exponential density of states (DOS). It is simple, symmetric and accurately describes the below-threshold, linear, and saturation regimes via a unique formulation. The model is eventually validated with the measurements of complementary OTFTs fabricated in a fullyprinted technology