The invention provides a multi-state sense amplifier, coupled to at least
one memory cell and a plurality of reference cells. The source follower,
coupled between a first node and the output terminal of the memory cell,
clamps the voltage drop across the memory cell to generate a memory cell
current flowing through the first node. The source follower circuit,
coupled between a plurality of second nodes and the output terminals of
the reference cells, clamps the voltage drops across the reference cells
to generate a plurality of reference currents respectively flowing
through the second nodes. The current mirror circuit, coupled to the
first node and the second nodes, duplicates the memory cell current of
the first node to affect the reference currents on the second nodes,
thereby generating a memory cell voltage on the first node and a
plurality of reference voltages on the second nodes.