The 74×139 (ex 74HC139) is a chip that contains two independent 2-to-4 line decoders/demultiplexers.
In this guide, you’ll learn the things you need to know about this chip in order to effectively use decoders and demultiplexers in your own projects.

What does the 74HC139 / 74LS139 do?
The 74×139 is a dual 2-to-4 line decoder/demultiplexer. This chip has two independent sections that can each take two binary inputs and turn them into four separate outputs.
Here’s how it works:
- Each section has two data inputs (let’s call them A and B) and four outputs (Y0 to Y3).
- Depending on the combination of A and B, one of the four outputs will be driven LOW, while the others remain HIGH.
- There is also an enable input for each section. The outputs are all HIGH if the enable input is not active.
This chip is useful when you want to select one of several signals or routes using binary signals, like in memory address decoding in computers.
How To Use This Chip
The 74HC139 comes in a 16-pin package, and you need to connect it to power before you can use it. Most 7400 ICs support a VCC voltage of 5V. One difference between the HC and LS version of the chip is that the 74HC139 supports 2V to 6V, while the 74LS139 only supports 5V.
74HC chips can normally supply a maximum of 4 mA from an output pin. If you’re using the 74LS version, the maximum current you can pull out of one output pin is 0.4 mA when the pin is high (sourcing) or 8 mA when the pin is low (sinking).
But these values can differ between models, so check the datasheet of your model to verify.

Build Something Useful This Evening
This gadget lets you use any IR remote-control to control your lamp, garden lights, heater oven, garage door, or anything else.
Once you’ve connected it to power, you can use the Demultiplexer/decoder inside.

74×139 Pinout
The 74×139 has 16 pins and contains two 1-of-4 inverting decoder/demultiplexer laid out as shown in the pinout diagram below:

Pin Name | Pin # | Type | Description |
---|---|---|---|
1EN | 1 | Input | Enable input for the first demultiplexer/decoder (active low). |
1S0 | 2 | Input | Selector input bit 0 for the first demultiplexer/decoder. |
1S1 | 3 | Input | Selector input bit 1 for the first demultiplexer/decoder. |
1Y0 | 4 | Output | Inverted output bit 0 from the first demultiplexer/decoder. |
1Y1 | 5 | Output | Inverted output bit 1 from the first demultiplexer/decoder. |
1Y2 | 6 | Output | Inverted output bit 2 from the first demultiplexer/decoder. |
1Y3 | 7 | Output | Inverted output bit 3 from the first demultiplexer/decoder. |
GND | 8 | Power | Connect to ground (GND). |
2Y3 | 9 | Output | Inverted output bit 3 from the second demultiplexer/decoder. |
2Y2 | 10 | Output | Inverted output bit 2 from the second demultiplexer/decoder. |
2Y1 | 11 | Output | Inverted output bit 1 from the second demultiplexer/decoder. |
2Y0 | 12 | Output | Inverted output bit 0 from the second demultiplexer/decoder. |
2S1 | 13 | Input | Selector input bit 1 for the second demultiplexer/decoder. |
2S0 | 14 | Input | Selector input bit 0 for the second demultiplexer/decoder. |
2EN | 15 | Input | Enable input for the second demultiplexer/decoder (active low). |
VCC | 16 | Power | Positive power supply. Connect to +5V power. |
Alternatives and Equivalents for 74HC139 / 74LS139
There are many versions of the 74×139 chip. They all have the same functionality, but with different specifications such as supported voltages and maximum current output.
Here’s a list of a few equivalents of this chip:
- 74HC139 (High-speed CMOS)
- 74HCT139 (High-speed CMOS, TTL compatible)
- 74LS139 (High-speed TTL)
- 74LVC139 (Low Voltage TTL)
- 74AC139 (Advanced CMOS)
- 74ALS139 (Advanced Low-Power Schottky TTL)
- 74F139 (Very High Speed)
- 74C139 (CMOS, similar to the 4000-series)
Some manufacturers also add a prefix, such as the SN74HC139 and SN74LS139 by Texas Instruments.
Can’t find the 74×139 anywhere? Then try one of the following IC alternatives:
- 74×137 – Dual 2-to-4 line decoder/demultiplexer.
- 74×138 – 3-to-8 line decoder/demultiplexer.
- 74×237 – Dual 2-to-4 line decoder/demultiplexer with address latches.
- CD4555 – Dual 1-of-4 line decoder/demultiplexer.
- CD4556 – Dual 1-of-4 line decoder with address latch.
If you can’t find the 74×139 IC in your local electronics store, don’t worry, you’ll most likely find it in one of the stores listed on this page of online stores where you’ll find components and tools for all your electronics projects.
Datasheet for the 74LS139 and 74HC139 chips
Download the PDF datasheet for your version of the 74×139 here:

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