The available catalogue of active-RC circuits has evolved by accumulation of knowledge derived largely by trial-and-error. In the process of developing analog tools for circuit design automation, it is important to follow systematic methodologies to obtain novel circuits. This book presents the research work of the authors toward a generalized symbolic framework for synthesis and modeling of analog active circuits using admittance matrix representations. The proposed generalized symbolic framework allows the description of all kinds of active building-blocks along with passive elements within a single nodal admittance matrix (NAM) based on the nodes of the circuit. The framework is functional at two main levels, i) active device level: using a systematic methodology that allows the derivation of ideal NAM representations based on pathological elements for all classes of active building-blocks and ii) circuit level: active-RC circuits targeting various applications can be synthesized systematically by applying admittance matrix expansion steps on the NAM using specific matrix operations, with the aid of the matrix elements representing active devices.