Four 2-to-1 digital multiplexers sharing one select line, in high-speed CMOS, SOIC-16. A single A/B select routes either the four A inputs or the four B inputs to the four Y outputs, and an active-low enable forces the outputs low. That makes it the easy way to switch a 4-bit bus between two sources: two data words into one, an address between two counters, or a display between two values. Cascade or stack them for wider buses. Runs 2-6 V.

Pinout

Pin	Name	Type	Function
1	A/B	input	Address select input (A/B, active-low means low selects A, high selects B). Standard CMOS input; when G is low, Y follows selected A or B input for all four channels.
2	1A	input	Channel 1 data input A. Routed to 1Y when A/B is low and G is low.
3	1B	input	Channel 1 data input B. Routed to 1Y when A/B is high and G is low.
4	1Y	output	Channel 1 data output. Drives the selected A or B input; forced low when G is high. ±6mA drive at 5V.
5	2A	input	Channel 2 data input A. Routed to 2Y when A/B is low and G is low.
6	2B	input	Channel 2 data input B. Routed to 2Y when A/B is high and G is low.
7	2Y	output	Channel 2 data output. Drives the selected A or B input; forced low when G is high.
8	GND	power_in	Ground reference, 0V. Continuous current through VCC or GND is limited to ±70mA (absolute max).
9	3Y	output	Channel 3 data output. Drives the selected A or B input; forced low when G is high.
10	3B	input	Channel 3 data input B. Routed to 3Y when A/B is high and G is low.
11	3A	input	Channel 3 data input A. Routed to 3Y when A/B is low and G is low.
12	4Y	output	Channel 4 data output. Drives the selected A or B input; forced low when G is high.
13	4B	input	Channel 4 data input B. Routed to 4Y when A/B is high and G is low.
14	4A	input	Channel 4 data input A. Routed to 4Y when A/B is low and G is low.
15	G	input	Output strobe, active low. When G is high, all four Y outputs are forced low regardless of A/B or data inputs; when G is low the mux operates normally.
16	VCC	power_in	Positive supply, 2V to 6V recommended (5V nominal). Absolute max 7V. Decouple with 0.1uF close to the pin.

Key specifications

Parameter	Value
Type	Quad 2-to-1 multiplexer
Channels	4 bits (2:1 each)
Select	one shared A/B line
Enable	active-low (forces Y low)
Outputs	true (non-inverting)
Logic family	HC (high-speed CMOS)
Supply voltage	2-6 V
Package	SOIC-16

Ordering variants

Same part, different packaging or reel option.

SN74HC157D (SOIC-16, tube)
SN74HC157DR (SOIC-16, tape & reel)

CAD (KiCad official)

Symbol: 74xx:74LS157 (pin-compatible with 74HC157)
Footprint: Package_SO:SOIC-16_3.9x9.9mm_P1.27mm
3D model: SOIC-16 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (37 pp, sha256 4dcd9386eac88c0e, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF