A demoludator circuit for demoludating a frequency modulated input signal comprises filter means (10) and detector means (14) for receiving a frequency modulated input signal and for providing a demoludated output signal, tuning means (19) for tuning the frequency characterictics of the filter means and of the detector means, and DC offset estimator means (18) wich are operable to estim ate the DC offset of the demoludated output signal, and to produce an offset signal representing the estimated DC offset, and to provide the offset signal to the tuning means. The tuning means are operable to tune the frequency characteristics of the filter means and detector means in dependence upon the offset signal.