Device Programmable CMOS Threshold Gate for Order Statistic Filtering

Threshold gates are the key elements of order statistic filtering. A (T/n) threshold gate outputs a. logic "1" if more than or equal to T of its n inputs are logic "1". Such a threshold gate can be realized by connecting n identical CMOS inverters with their outputs wired together and sensed by a buffering inverter. The circuit, performs threshold decision in small area with fast speed. An inherent limitation is on the number of inputs. An incremental scheme is proposed to construct threshold gate networks for general threshold decision. Standard, weighted, and multi-stage order statistic filters can be realized by the threshold gates or threshold gate networks.