A non-linearity evaluation circuit for use with a signal generator having at least a partly non-linear operation. The non-linearity evaluation circuit may include a detection unit operable to detect a given amplitude attribute in a target signal generated by the signal generator, a time position of the amplitude attribute in the target signal defining a time location of a snapshot time window relative to the target signal, a part of the target signal occupying the snapshot time window being a corresponding signal snapshot, and a presence of the given amplitude attribute indicating that the signal snapshot includes noise due to the non-linear operation of the signal generator. The non-linearity evaluation circuit may further include a controller operable to analyse the signal snapshot rather than a larger part of the target signal and to evaluate the non-linear characteristics of the operation of the signal generator based on the analysis.