Patent ID: 7286429

Claim:
A circuit for sensing a resistance state of a memory cell, the memory cell being capable of switching between a high resistance state and a low resistance state, comprising: a high reference cell in high resistance state; a low reference cell in low resistance state; a voltage supply for applying a predetermined voltage to the memory cell to generate an output current; a set of differential amplifiers selectively coupled to the memory cell and the high and low reference cells; and a sense amplifier coupled to the differential amplifiers, wherein the resistance of the high reference cell in high resistance state has a first margin of difference from the resistance of the memory cell in high resistance state the first margin of difference being determined by difference in area between the memory cell and the high reference cell, and wherein the resistance of the low reference cell in low resistance state has a second margin of difference from the resistance of the memory cell in low resistance state the second margin of difference being determined by difference in area between the memory cell and the low reference cell.