SEMICONDUCTOR ARITHMETIC UNIT

摘要

PROBLEM TO BE SOLVED: To perform a maximum or minimum value retrieval operation fast and also with high accuracy with respect to a vector quantization processor by adjusting the current drive capability of a multiple loop circuit in accordance with the change of an output of a logical operation circuit. SOLUTION: A differential absolute value distance signal 601 is stored as an electric charge on respective floating gates 602 of aνMOS comparator 603. An output of an OR gate 608 is fed back to a reference voltage signal input terminal 612 of all comparators 603 through variable resistor 611 that is controlled by a high gain amplifier 609 and a controller 610. They forms a ring oscillator of a multiple loop. A current drive capability that drives input capacitance of the comparators 603 is changed by switching the value of the resistor 611 and a sweep speed of reference voltage VR is controlled. The sweep speed of the VR is successively reduced by increasing the value of the resistor 611 gradually and retrieval accuracy is increased little by little.