74HC257 Quad 2-input multiplexer IC

The 74HC257 is a high-performance CMOS quad 2-input multiplexer that packages four independent 2-to-1 data selectors plus a common select input and a 3-state output enable. Each section selects between its A and B input pair and presents the selected signal on the corresponding Y output. Built in the ’HC family, the device combines low static power consumption with switching speeds suitable for bus-oriented systems and medium-speed logic.

Designed for bus interfacing and source-selection tasks, the 74HC257’s three-state outputs let multiple devices share a common bus without loading it when output enable (G) is asserted high. The chip accepts standard CMOS input levels across a wide supply range and is pin-compatible with related HC logic, easing substitution and mixed-family designs. Typical use includes routing data lines, selecting between memory or peripheral sources, and simple data-path multiplexing.

Available in PDIP, SOIC, TSSOP and other packages with industry-standard pinouts, the 74HC257 is commonly used where compact, deterministic selection of parallel signals is required. Its low input currents and guaranteed noise margins make it a dependable building block for embedded systems, address/data multiplexing, and multi-source bus architectures.