We present a methodology for model-based diagnosis of analog circuits using the constraint logic programming approach. Presented methodology stems from our earlier work on the diagnosis of active analog filters by using CLP(R)and has the following major improvements: modeling of the diagnosed circuit is generalized to arbitrary analog circuits consisting of linear elements (non-linear circuits are included by piecewise linearisation of their characteristics); both hard and parametric faults are considered in the diagnostic process; fault situations with multiple-hard-and-single-parametric faults can be diagnosed. Examples are given to illustrate the approach.