The following work is concerned with the design of analog circuits based on organic field-effect transistors (OFETs). A capital point is the utilization of an adequate transistor model portraying the complex nature of such semiconductor devices with a satisfying degree of accuracy. Noting that existent MOSFET models based on inorganic semiconductors (Si) cannot fulfill this task with the required precision demanded in OFET-based analog circuit design, a novel transistor model using numerical and physical considerations was developed from the ground up. Such a model maps the voltage-current characteristics of a typical transistor geometry on parametrical functions using a nonlinear fitting algorithm. Specifically, a reference curve is vertically and horizontally stretched by means of the mutual modulation of three functions according to the actual electrode voltages. Further transistor geometries are obtained through traditional transistor scaling. The overall OFET model also includes: (i) a simple MOSFET capacitance model, (ii) a statistical model that reflects the process fluctuations from transistor to transistor (voltage-current (UI) characteristic variability), and (iii) a hysteresis model based on an RC-network.