Patent ID: 6691145
Filing Date: 2004-02-10
Classification: G06G,G11C,H04N

Abstract:
A computing circuit for computing an absolute difference between a first signal and a second signal, comprising:a large input selection circuit which compares said first and second signals and outputs whichever signal is larger in signal value; a small input selection circuit which compares said first and second signals and outputs whichever signal is smaller in signal value; and a subtraction circuit for subtracting the output of said small input selection circuit from the output of said large input selection circuit, wherein said subtraction circuit comprises: a capacitor; a first switch provided between a first terminal of said capacitor and the output of said large input selection circuit; a second switch provided between the first terminal of said capacitor and the output of said small input selection circuit; and a third switch provided between a second terminal of said capacitor and a terminal connected to a prescribed potential, and wherein: the absolute difference between said first signal and said second signal is output from said second terminal of said capacitor by first turning said first switch off and said third switch on, then turning said second switch on, and thereafter turning said third switch off, then turning said second switch off, and finally turning said first switch on.