7400 Series Guide: 74HC15/74LS15 (3-input AND gates)

The 74×15 (ex 74LS15) is a cool little chip that has three 3-input open-collector AND gates. An open collector output allows for easy interfacing with chips of different logic levels, although swapping it with a standard AND gate chip isn’t straightforward

In this guide, you will learn everything you need to know about this chip and how you can use AND gates in your own projects.

What does the 74HC15 / 74LS15 do?

The 74×15 gives you three 3-input open-collector AND gates that you can use individually. An AND gate is a logic gate that outputs 1 (HIGH) only if all of its inputs are 1 (HIGH).

In the truth table below, you can see what the output will be for any given input:

Input A	Input B	Input C	Output Q
0	0	0	0
0	0	1	0
0	1	0	0
0	1	1	0
1	0	0	0
1	0	1	0
1	1	0	0
1	1	1	1

How To Use This Chip

The 74×15 comes in a 14-pin package, and you need to connect its power pins before you can use it. Most versions of this IC will support a VCC voltage of 5V.

This chip uses open-collector outputs which means you can only sink current, not source it.

The output of each gate in the 74H15 can sink around 20 milliamps. The 74LS15 can usually handle only 8 milliamps of current. However, these values can change depending on the chip manufacturer.

74×15 Pinout

The 74×15 has 14 pins and contains three 3-input open-collector AND gates laid out as shown in the pinout diagram below:

Pin #	Type	Description
1	Input	Input to the first AND gate.
2	Input	Input to the first AND gate.
3	Input	Input to the second AND gate.
4	Input	Input to the second AND gate.
5	Input	Input to the second AND gate.
6	Output	Open-collector output from the second AND gate.
7	Power	Connect to ground (GND).
8	Output	Open-collector output from the third AND gate.
9	Input	Input to the third AND gate.
10	Input	Input to the third AND gate.
11	Input	Input to the third AND gate.
12	Output	Open-collector output from the first AND gate.
13	Input	Input to the first AND gate.
14	Power	Positive power supply (VCC). Connect to +5V power.

Alternatives and Equivalents for 74LS15

There are many versions of the 74×15 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:

• 74HC15 (High-speed CMOS)
• 74HCT15 (High-speed CMOS, TTL compatible)
• 74LS15 (High-speed TTL)
• 74LVC15 (Low Voltage TTL)
• 74AC15 (Advanced CMOS)
• 74ALS15 (Advanced Low-Power Schottky TTL)
• 74F15 (Very High Speed)
• 74C15 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC15 and SN74LS15 by Texas Instruments.

Can’t find the 74×15 anywhere? Then try one of the following IC alternatives:

• 74×11 – Triple 3-input open-collector AND gates
• CD4073 – Triple 3-input open-collector AND gates

If you can’t find the 74×15 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 74×15 chip

Download the PDF datasheet for your version of the 74×15 here:

• 74LS15 National Semiconductor