1 x 3:8 decoder/demultiplexer in 16-SOIC
The SN74HCT138DR is a single 3-to-8 line decoder/demultiplexer from the 74HCT logic family, packaged in a 16-SOIC (0.154", 3.90mm width) surface-mount package. It accepts a 3-bit binary address input and activates one of eight mutually exclusive active-low outputs, making it a standard building block for memory address decoding, data routing, and chip-select generation in 5V digital systems.
Supply range and output drive
The 4mA source and 4mA sink capability at the outputs is modest — sufficient for driving CMOS logic inputs or low-power loads, but not designed for high-fanout or LED drive without a buffer. For a decoder handling address lines in a 5V control board, the 74HCT family's TTL-compatible inputs simplify interfacing with legacy 5V logic without external level translation.