A new nullor-based model to describe the behavior of Operational Transresistance Amplifiers (OTRAs) is introduced. The new model is composed of four nullors and three grounded resistors. As a consequence, standard nodal analysis can be applied to compute fully-symbolic small-signal characteristics of OTRA-based analog circuits, and the nullorbased OTRAs model can be used in CAD tools. In this manner, the fully-symbolic transfer functions of several application circuits, such as filters and oscillators can easily be approximated.