The LS139 is a high speed dual 1-of-4 decoder/ demultiplexer fabricated with the Schottky barrier diode process. The device SN74LS139N has two independent decoders, each of which accept two binary weighted inputs (A0, A1) and provide four mutually exclusive active LOW outputs (O0O3). Each decoder has an active LOW Enable (E). When E is HIGH all outputs are forced HIGH. The enable can be used as the data input for a 4-output demultiplexer application.
Each half of the LS139 generates all four minterms of two variables. These four minterms are useful in some applications, replacing multiple gate functions as shown in Fig. a, and thereby reducing the number of packages required in a logic network.