SIGNAL READING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a signal reading circuit by which signals having various intervals of two kinds and more than three kinds are exactly demodulated even though the rotating speed of a disk is not strictly controlled. SOLUTION: This circuit is provided with: an edge detecting circuit 1 for detecting the rising edge of an input signal; a period detecting circuit 2 for successively detecting the period of the edge successively detected with the edge detecting circuit 1; a reference width circulating circuit 3 for performing a preliminarily decided arithmetic operation by using the period of the edge successively detected with the period detecting circuit 2 to calculate the reference width; and a demodulation circuit 4 for performing a preliminarily decided arithmetic operation by using the reference width calculated with the reference width calculating circuit 3 with respect to the period of the edge successively detected with the period detecting circuit 2 and performing the demodulation in accordance with this arithmetic result.