The SN74HC139 device is designed for high-performance memory-decoding or data-routing applications requiring very short propagation delay times. In high-performance memory systems, this decoder can minimize the effects of system decoding. When employed with high-speed memories utilizing a fast enable circuit, the delay time of this decoder and the enable time of the memory usually are less than the typical access time of the memory. This means that the effective system delay introduced by the decoder is negligible.

The SN74HC139 device comprises two individual 2-line to 4-line decoders in a single package. The active-low enable G input can be used as a data line in demultiplexing applications. This decoder/demultiplexer features fully buffered inputs, each of which represents only one normalized load to its driving circuit.