1-of-8 decoder/demux in a 16-pin DIP
The Texas Instruments SN74ALS138AN is a single 3-line to 8-line decoder/demultiplexer from the 74ALS family. It takes a 3-bit binary input and asserts one of eight active-low outputs — the standard address-decoding or data-routing block for 5V logic boards. The 16-pin DIP (0.300-inch wide, 7.62 mm pitch) is through-hole only, so it fits legacy sockets, protoboards, and point-to-point wiring but not modern SMT reflow. Output drive is asymmetric: 400 µA sourcing, 8 mA sinking. Not rated for industrial enclosures, engine bays, or outdoor telecom cabinets without additional screening or conformal coating.
TI lists the SN74ALS138AN as Active.
What the output drive means for your board
The 400 µA high-level output current and 8 mA low-level output current are typical for ALS logic — the high side is weak. If you're decoding addresses for a memory chip or selecting a peripheral, the load is almost always CMOS or TTL inputs, so the sink current is what matters. If you need to drive a relay coil, LED, or long trace, add a buffer or transistor stage. The 8 mA sink is enough for one or two standard LS/ALS inputs but not for a fan-out of ten.