Precision Multi-Input Current Comparator and Its Application to Analog Median Filter Implementation

In this work, a simple architecture of a precision CMOS multi-input current comparator is proposed. The circuit is based on the usage of a multi-input current Max circuit. The inherent corner error of the Max circuit is eliminated, using a feedback circuit, increasing thus the precision of the comparator. Only the digital output corresponding to the maximum (or minimum) input current is at logic 1, while the other outputs are at logic 0. An application of the comparator to the analog implementation of a current-mode median filter is also presented. A five-input comparator and a three-input median filter were fabricated using double-poly double-metal 2 m CMOS MIETEC technology. Experimental results are given, to validate the theoretical analysis and to demonstrate the feasibility and the precision of the proposed circuits.