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. Supply range is 4.5 V to 5.5 V, single-rail. Output drive is asymmetric: 400 µA sourcing, 8 mA sinking. Temperature grade is commercial: 0°C to 70°C. Not rated for industrial enclosures, engine bays, or outdoor telecom cabinets without additional screening or conformal coating.
Active lifecycle — no LTB watch needed
TI lists the SN74ALS138AN as Active. For a BOM line that needs a through-hole 3:8 decoder, there's no imminent obsolescence risk to plan around.
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.