1-of-8 decoder/demultiplexer for address decoding and data routing
The CD74HCT138M is a single 3-to-8 line decoder/demultiplexer from the 74HCT logic family. It takes a 3-bit binary input and selects one of eight active-low outputs. The HCT input thresholds are TTL-compatible, so it can be driven by 5 V logic outputs without level translation.
Output drive and supply considerations
That is enough to drive a single LSTTL load or a CMOS gate input directly, but for heavier fan-out — multiple loads or longer traces — a buffer stage is advisable. The 4 mA figure is the same for both high and low states, so the drive is symmetrical. The 4.5 V minimum supply means this part will not run reliably at 3.3 V. If your design uses a 3.3 V rail, look at the 74LV or 74LVC series for a 3.3 V–compatible decoder. At 5 V ±10 % it is solid.
Package and board-level fit
Shipping medium is tube. If your pick-and-place line expects tape-and-reel, verify the reel option (often the same die in a different order code suffix). The 16-SOIC package is MSL 1 typically, but confirm the bake requirements if the tube seal is broken.
Lifecycle and sourcing posture
ROHS3 compliant. No LTB risk on this code today.