7400 Series Guide: 74HC147/74LS147 (10-to-4 priority encoder)

The 74×147 (ex 74LS147) is a chip that functions as a 10-line to 4-line priority encoder. It prioritizes inputs from highest to lowest, providing a 4-bit coded output corresponding to the highest-priority active input.

In this guide, you’ll learn the things you need to know about this chip in order to use priority encoding in your own projects.

What does the 74HC147 / 74LS147 do?

The 74×147 is a 10-to-4 priority encoder. It takes up to 10 input signals, labeled from 0 to 9, and converts them into a 4-bit binary output. The “priority” part means that if more than one input is active at once, the chip will give priority to the input with the highest number.

For instance, if both inputs 3 and 6 are active, the output will correspond to input 6 because it has a higher priority.

Priority encoders like the 74×147 are often used in systems that need to handle multiple input signals and decide which one to process based on priority.

How To Use This Chip

The 74HC147 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 74HC147 supports 2V to 6V, while the 74LS147 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.

Once you’ve connected it to power, you can use the Priority encoder inside.

74×147 Pinout

The 74×147 has 16 pins and contains 10-to-4 line inverting priority encoder laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
A4	1	Input	Active low input for pin A4 to the priority encoder.
–	2	NC	Not connected.
A6	3	Input	Active low input for pin A6 to the priority encoder.
A7	4	Input	Active low input for pin A7 to the priority encoder.
A8	5	Input	Active low input for pin A8 to the priority encoder.
Y2	6	Output	Output bit Y2 from the priority encoder.
Y1	7	Output	Output bit Y1 from the priority encoder.
GND	8	Power	Connect to ground (GND).
Y0	9	Output	Output bit Y0 from the priority encoder.
A9	10	Input	Active low input for pin A9 to the priority encoder.
A1	11	Input	Active low input for pin A1 to the priority encoder.
A2	12	Input	Active low input for pin A2 to the priority encoder.
A3	13	Input	Active low input for pin A3 to the priority encoder.
Y3	14	Output	Output bit Y3 from the priority encoder.
–	15	NC	Not connected.
VCC	16	Power	Positive power supply. Connect to +5V power.

Alternatives and Equivalents for 74HC147 / 74LS147

There are many versions of the 74×147 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:

• 74HC147 (High-speed CMOS)
• 74HCT147 (High-speed CMOS, TTL compatible)
• 74LS147 (High-speed TTL)
• 74LVC147 (Low Voltage TTL)
• 74AC147 (Advanced CMOS)
• 74ALS147 (Advanced Low-Power Schottky TTL)
• 74F147 (Very High Speed)
• 74C147 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC147 and SN74LS147 by Texas Instruments.

Can’t find the 74×147 anywhere? Then try one of the following IC alternatives:

• 74×148 – 8-to-3 line priority encoder.
• 74×151 – 8-input multiplexer with 3-bit select.
• 74×153 – Dual 4-input multiplexer.
• CD4532 – 8-input priority encoder.

If you can’t find the 74×147 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 74LS147 and 74HC147 chips

Download the PDF datasheet for your version of the 74×147 here:

• 74LS147 (Futurlec)
• CD74HC147 (Texas Instruments)
• MC74HC147 (Motorola)
• SN74LS147 (Texas Instruments)