Nonvolatile memory sensing circuit including variable current source

A nonvolatile memory device comprising a plurality of memory slices, each memory slice including one or more memory sectors and a read circuit for sensing a resistance state of a magnetic memory cell in said one or more memory sectors, said read circuit comprising:

• a first input node through which a reference current passes;
• a second input node through which a read current from said one or more memory sectors passes;
• a sense amplifier configured to compare input voltages, said sense amplifier having first and second input terminals with said second input terminal connected to said second input node;
• a reference resistor connected to said first input node at one end and said first input terminal of said sense amplifier at the other end;
• a variable current source connected to said reference resistor at one end and ground at the other end;
• and
• a second current source connected to said second input node at one end and ground at the other end,
• wherein each of said one or more memory sectors includes a column of transistors, at least one row of transistors, and an array of magnetic memory cells arranged in rows and columns, each of said magnetic memory cells including an access transistor and a magnetic tunnel junction (MTJ) coupled in series between a respective one of a plurality of source lines and a respective one of a plurality of bit lines, each transistor of said at least one row of transistors being directly coupled to another respective one of said plurality of source lines at one of source and drain and another respective one of said plurality of bit lines at the other one of source and drain.