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SN74HC138

Public Made by Adom

by adom

TI 3-to-8 line decoder/demultiplexer, SOIC-16. Three enables, eight active-low outputs, HC CMOS 2-6 V. Datasheet-verified.

componentlogicdecoderdemultiplexer74hcsoic-16texas-instruments
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SN74HC138

Texas Instruments · 3-to-8 line decoder / demux · SOIC-16

A 3-to-8 line decoder/demultiplexer in high-speed CMOS, SOIC-16. Three binary select inputs (A, B, C) drive eight mutually exclusive active-low outputs (Y0-Y7): the addressed output goes low while the other seven stay high. Three enable inputs (G1 active-high, G2A and G2B active-low) gate the whole device, which makes it easy to chain several for wider address decoding or to use as a 1-of-8 demultiplexer for a data line. Runs 2-6 V.

Pinout

Pin Name Type Function
1 A input Select input A (least significant bit of the 3-bit binary address selecting which Y output is asserted low).
2 B input Select input B (middle bit of the 3-bit binary address).
3 C input Select input C (most significant bit of the 3-bit binary address).
4 G2A input Active-low enable A. Must be low (together with G2B low and G1 high) to enable outputs; otherwise all Y outputs are forced high.
5 G2B input Active-low enable B. Must be low (together with G2A low and G1 high) to enable outputs.
6 G1 input Active-high enable. Must be high (together with G2A and G2B low) to enable outputs.
7 Y7 output Decoded output 7 (most significant, active low). Asserts low when enabled and CBA = 111. Drive capability ±4 mA at VCC = 5 V.
8 GND power_in Ground reference (0 V).
9 Y6 output Decoded output 6 (active low). Asserts low when enabled and CBA = 110.
10 Y5 output Decoded output 5 (active low). Asserts low when enabled and CBA = 101.
11 Y4 output Decoded output 4 (active low). Asserts low when enabled and CBA = 100.
12 Y3 output Decoded output 3 (active low). Asserts low when enabled and CBA = 011.
13 Y2 output Decoded output 2 (active low). Asserts low when enabled and CBA = 010.
14 Y1 output Decoded output 1 (active low). Asserts low when enabled and CBA = 001.
15 Y0 output Decoded output 0 (least significant, active low). Asserts low when enabled and CBA = 000.
16 VCC power_in Positive supply voltage, 2 V to 6 V (nominal 5 V).

Key specifications

Parameter Value
Type 3-to-8 decoder / demultiplexer
Select inputs 3 (A/B/C)
Outputs 8 active-low (Y0-Y7)
Enables G1 (high) + G2A/G2B (low)
Logic family HC (high-speed CMOS)
Supply voltage 2-6 V
Package SOIC-16
Body (L×W×H) 9.9 × 3.9 × 1.75 mm

Ordering variants

Same part, different packaging or reel option.

  • SN74HC138D (SOIC-16, tube)
  • SN74HC138DR (SOIC-16, tape & reel)

CAD (KiCad official)

  • Symbol: 74xx:74HC138
  • Footprint: Package_SO:SOIC-16_3.9x9.9mm_P1.27mm
  • 3D model: SOIC-16 (KiCad packages3D)
  • 3D model files: sn74hc138-etched.step / sn74hc138-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); sn74hc138.step / sn74hc138.glb are the bare package body.

Provenance

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

  • Datasheet: Texas Instruments datasheet (35 pp, sha256 ba6cab88a44c1c9a, 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