This thesis investigates the design of single transistor second order active filters. Four general topologies are presented, each with a two port network surrounded by three impedances that form a T-network. From the topologies, four transfer functions are derived which are further simplified by replacing the two port transmission matrix parameters with those of an ideal MOS. An exhaustive MAPLE search code is used to generate all possible second order filters. The search is carried out on the four general transfer functions, considering all possible impedance combinations. Design procedures of selected filters are shown and verified by Cadence Spectre simulations and experimental measurements. Based on the single transistor second order filters, active realizations of higher order filters are explored. A fourth order bandpass Chebyshev filter and a fourth order Comb filter are presented. Simulation and experimental results of the designed filters are shown and compared with the theoretical ones.