A device for detecting the peak value of a signal with crest factor not known a priori includes a pair of peak detectors, each of which includes a rectifier element and a discharge-current generator and generates a respective output signal that is a function of the ratio between a physical dimension of the rectifier element and the intensity of discharge current produced by the generator. The ratio is different for the two detectors, and a combination network combines the output signals of the two peak detectors with one another and produces a combined signal indicating the peak value sought with high accuracy.