A signal-processing circuit has a first and a second input, which receive a first and a second differential signal, a third input, which receives a common-mode signal, the first and second differential signals having an equal and substantially opposite trend with respect to the common-mode signal, and a first output supplying a first processed signal, equivalent to the first differential signal rectified with respect to the common-mode signal, and satisfying throughout its course a first relation of comparison with the common-mode signal. The processing circuit is provided with first formation means for formation of the first processed signal, which operate on the basis of the first differential signal, and second formation means for formation of the first processed signal, which operate on the basis of the second differential signal; the first and second formation means co-operate in the formation of the first processed signal.