US Patent 7352640 High-speed, self-synchronized current sense amplifier

A sense amplifier circuit and a method for reading a memory cell. A circuit comprises a first bit line associated with a memory cell. A first input of a latch is coupled to the first bit line and a second input of the latch is coupled to a second node. There is a means for biasing the first input and the second input of the latch to a differential voltage between the first node coupled to the first bitline and the second node. There is also a means for switching the latch according to memory cell current. There is also a means for producing an output signal indicating the direction of switch. A method of reading a memory cell comprises precharging a first bit line which is associated with a memory cell. The memory cell current is driven according to the programmed state of the memory cell. Latch circuitry is biased based on a differential voltage between a first node coupled to the first bit line and a second node. The latch circuitry is then activated and the latch circuitry switches according to the memory cell current. An output signal indicating the direction of the latch circuitry's switch is then produced.