Patent ID: 7778065

Claim:
An apparatus for sensing the data state of a multiple level, programmable resistive memory device, comprising: an active clamping device connected to a data leg that is selectively coupled a programmable resistive memory element, the active clamping device configured to clamp a fixed voltage, at a first node of the data leg, across the programmable resistive memory element, thereby establishing a fixed current sinking capability thereof; and a plurality of differential amplifiers, each of the plurality of differential amplifiers configured to compare a first voltage input, taken at a second node of the data leg, with a second voltage input; wherein the second voltage input for each differential amplifier comprises different reference voltages with respect to one another so as to enable each differential amplifier to detect a different resistance threshold, thereby determining a specific resistance state of the programmable resistive memory element; a set of reference legs, each associated with one of the differential amplifiers, each reference leg configured to conduct a reference current therethrough, wherein the reference voltage for a given differential amplifier is taken a node in the specific reference leg associated therewith; each reference leg further including an adjustable input current source associated therewith, wherein reference currents in each of the reference legs are configured to have different gains with respect to the input current source; and each reference leg further including an individual output impedance stage configured for precise control of the reference current therein.