An 8-to-3 line priority encoder in high-speed CMOS, SOIC-16, the inverse of a decoder. It takes eight active-low inputs and outputs the 3-bit binary number of the highest-numbered one that is active, ignoring lower ones (the priority part). That turns a bank of buttons, interrupt lines, or switches into a compact binary code a microcontroller can read on three pins. Enable-in (EI), enable-out (EO), and group-select (GS) let you cascade two devices into a 16-to-4 encoder. Runs 2-6 V. The KiCad 74LS148 symbol shipped here is pin-identical.

Pinout

Pin	Name	Type	Function
1	4	input	Active-low data input 4. Requests encoding of octal value 4 when asserted (LOW).
2	5	input	Active-low data input 5. Requests encoding of octal value 5 when asserted (LOW).
3	6	input	Active-low data input 6. Requests encoding of octal value 6 when asserted (LOW).
4	7	input	Active-low data input 7 (highest priority). Requests encoding of octal value 7 when asserted (LOW).
5	EI	input	Active-low enable input. All outputs are forced to their inactive (HIGH) state when EI is HIGH; encoding is enabled when EI is LOW. Used for cascading multiple stages.
6	A2	output	Active-low encoded output bit 2 (MSB of the 3-bit octal code). Drives ±4 mA at Vcc = 5 V.
7	A1	output	Active-low encoded output bit 1. Drives ±4 mA at Vcc = 5 V.
8	GND	power_in	Ground reference (0 V).
9	A0	output	Active-low encoded output bit 0 (LSB of the 3-bit octal code). Drives ±4 mA at Vcc = 5 V.
10	0	input	Active-low data input 0 (lowest priority). Requests encoding of octal value 0 when asserted (LOW) and no higher-numbered input is active.
11	1	input	Active-low data input 1. Requests encoding of octal value 1 when asserted (LOW).
12	2	input	Active-low data input 2. Requests encoding of octal value 2 when asserted (LOW).
13	3	input	Active-low data input 3. Requests encoding of octal value 3 when asserted (LOW).
14	GS	output	Active-low group-select output. Goes LOW whenever any data input (0-7) is active and EI is LOW, indicating that a valid encoded value is present on A0-A2.
15	EO	output	Active-low enable output. Goes LOW when EI is LOW and no data input is asserted, signaling downstream cascaded encoders that they may drive the outputs.
16	VCC	power_in	Positive supply, 2 V to 6 V (5 V nominal). Icc max 80 µA.

Key specifications

Parameter	Value
Type	8-to-3 priority encoder
Inputs	8 active-low (0-7)
Outputs	3-bit binary (A0-A2, active-low)
Priority	highest active input wins
Cascade	EI / EO / GS pins
Logic family	HC (high-speed CMOS)
Supply voltage	2-6 V
Package	SOIC-16

Ordering variants

Same part, different packaging or reel option.

SN74HC148D (SOIC-16, tube)
SN74HC148DR (SOIC-16, tape & reel)

CAD (KiCad official)

Symbol: 74xx:74LS148 (pin-compatible with 74HC148)
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 (25 pp, sha256 ca65b15c3841afab, 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