The research is concerned with the identification and inversion of weak nonlinear behaviour occurring in analog integrated circuits for ADSL applications. The nonlinear behaviour induced by the nonlinear characteristics of the analog components of the integrated circuits, is limiting the performance of the overall ADSL data transmission system. Thus, the goal is to compensate the inherent nonlinearities of the circuit. This nonlinear equalization should be realized in the digital domain, through adaptive nonlinear filters. Nonlinear system identification serves as a starting point for the analysis of the inversion of nonlinear systems. Through the identification of a discrete time nonlinear model of the analog circuit, a thorough analysis of the adaptive nonlinear equalization is made possible. Furthermore, the digital nonlinear model can then be implemented in a discrete time simulation platform for the evaluation of the achievable transmission rate of the entire ADSL system.