For realizing high speed one time programmable memory, bit line is multi-divided for reducing capacitance, so that the bit line is quickly charged when reading and multi-stage sense amps are used for connecting divided bit line, wherein the multi-stage sense amps are composed of a first dynamic circuit serving as a local sense amp for reading the memory cell, a second dynamic circuit serving as a segment sense amp for reading the local sense amp, and a tri-state inverter serving as an amplify circuit of a global sense amp for reading the segment sense amp. When reading data, a voltage difference in the bit line is converted to a time difference for differentiating high data (programmed) and low data (unprogrammed) by the multi-stage sense amps. And buffered data path is connected to the global sense amp for realizing fast data transfer. Additionally, alternative circuits and memory cell structures are described.