There is one sense amplifier for each column of memory cells, so there are usually hundreds or thousands of identical sense amplifiers on a modern memory chip.
For example, in memory chip fabrication there are some 30 lithography steps, 10 oxidation steps, 20 etching steps, 10 doping steps, and many others are performed.
One way to build such binary sensors is to modify standard memory chip technology, where each memory bit cell is designed to be sensitive to visible light.