Low voltage analog median filters implementation

Median filters are very important non-linear filters, finding many applications in speech and image processing. Last years analog implementation of non-linear filters has gained new interest. In this work, two new low voltage analog CMOS current-mode median circuits are proposed. In the circuit design current-mode circuits are used, such current window comparator circuit and current mode min/max selectors. A zero-threshold voltage floating gate MOS transistor is proposed to convert voltage to current in case of voltage inputs. This transistor ensures very low supply voltage operation of the circuits and in the same time the circuits can operate with rail-to-rail voltages. Simulation results using AMS 0.35 μm n-well CMOS technology confirm the theoretical analysis and demonstrate the feasibility of the circuits.