The CD74ACT540E is an 8-bit inverting buffer with 3-state outputs from the 74ACT family. It takes eight input signals, inverts them, and drives the results onto a shared bus — the 3-state outputs let you disconnect the buffer from the bus when the output-enable pin is deasserted, which is the standard way to build a bidirectional data path without contention. The 74ACT series uses an advanced CMOS process that combines the speed of bipolar 74F logic with the low power of CMOS, so this part switches fast enough for most 5 V microprocessor and DSP interfaces while drawing far less quiescent current than a bipolar buffer.
If your board runs a 3.3 V core with a 5 V I/O plane, this buffer sits on the 5 V side. For a ground-based industrial controller that stays indoors, the extra temperature headroom is free margin.
Output drive and 3-state control
The 3-state control is active-low on the CD74ACT540E — when the output-enable pin is low, the outputs follow the inverted inputs; when high, the outputs go high-impedance. This lets multiple buffers share a bus without fighting each other.
Package and mounting — through-hole DIP
That makes it easy to breadboard, hand-wire, or socket in a legacy PCB. The supplier device package is 20-PDIP. If your assembly line is entirely SMT, you will want the surface-mount variant (CD74ACT540M or similar) — but for prototyping, repair, or low-volume builds where hand-soldering is the norm, the DIP is the practical choice.