74HC138 3-to-8 Line Decoder / Demultiplexer
3-to-8 line decoder with active-low outputs. Three enable inputs (two active-low ~G2A/~G2B, one active-high G1) allow easy cascading. Complement of 74HC238 (active-high outputs).
Aliase:SN74HC138N, 74HCT138, 3-to-8 Demux, Inverting Decoder
DIP-16 Top View
16 Pins
Pinout Table16
| Pin | Signal / Name | Type | Alternative Functions |
|---|---|---|---|
| 1 | A | Digital | Address Select Input A (LSB) |
| 2 | B | Digital | Address Select Input B |
| 3 | C | Digital | Address Select Input C (MSB) |
| 4 | ~G2A | Digital | Enable Input 2A (Active Low — must be LOW to enable outputs) |
| 5 | ~G2B | Digital | Enable Input 2B (Active Low — must be LOW to enable outputs) |
| 6 | G1 | Digital | Enable Input 1 (Active High — must be HIGH to enable outputs) |
| 7 | ~Y7 | Digital | Decoded Output Y7 (Active Low, selected when CBA = 111) |
| 8 | GND | Ground | System Ground (0V) |
| 9 | ~Y6 | Digital | Decoded Output Y6 (Active Low, selected when CBA = 110) |
| 10 | ~Y5 | Digital | Decoded Output Y5 (Active Low, selected when CBA = 101) |
| 11 | ~Y4 | Digital | Decoded Output Y4 (Active Low, selected when CBA = 100) |
| 12 | ~Y3 | Digital | Decoded Output Y3 (Active Low, selected when CBA = 011) |
| 13 | ~Y2 | Digital | Decoded Output Y2 (Active Low, selected when CBA = 010) |
| 14 | ~Y1 | Digital | Decoded Output Y1 (Active Low, selected when CBA = 001) |
| 15 | ~Y0 | Digital | Decoded Output Y0 (Active Low, selected when CBA = 000) |
| 16 | VCC | Power | Positive Power Supply (2–6V) |