LEVEL CHANGE DETECTOR OF ANALOG SIGNAL

PURPOSE:To detect a minute decrease in a high part of a signal and a minute increase in a low part of the signal, by providing a high and a low threshold value, discriminating analog signals respectively and synthesizing both discriminating signals so as to include all required information. CONSTITUTION:A signal (a) is discriminated at a comparator 6 by taking a high reference voltage b1 as a threshold value and becomes a signal c1, and at a comparator 7 by taking a comparatively lower reference voltage b2 as a threshold value and becomes a signal c2. A front edge detection circuit 8 detects the front edge of the signal c1 and outputs a pulse signal (f), and a tail edge detection circuit 9 detects the rear edge of the signal c2 and outputs a pulse signal (g). A flip-flop circuit 10 receives the pulse signal (f) at the set input and the pulse signal (g) at the reset input side, and outputs pulse signals (h), (i). Logical product and sum outputs are obtained with AND circuits 11, 12 and an OR circuit 13 and a pulse signal (l) is outputted.