7400 Series Guide: 74HC74/74LS74 (Dual D Flip-Flop)

The 74×74 (ex 74HC74) is a chip that comes packed with two D flip-flops with set and reset.

Learn how it works and how to use it with this beginner-friendly guide and start using D flip-flops in your projects.

What does the 74HC74 / 74LS74 do?

The 74×74 gives you two D flip-flops that you can use individually. A D flip-flop is small circuit that can store one bit.

It is commonly used as a basic building block in digital electronics to create counters or memory blocks such as shift registers.

You can also use it to make fun stuff like a coin tosser game by connecting the inverted output to the D input and having a fast, button-controlled clock signal.

How To Use This Chip

The 74HC74 comes in a 14-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 74HC74 supports 2V to 6V, while the 74LS74 only supports 5V.

Once you’ve connected it to power, you can use any of the two D flip-flop with set and reset inside.

Output Current

The 74HC74 supports an output current of around 4 mA.

For the 74LS74, the maximum current you can pull out of one output pin is only 0.4 mA when the pin is high (sourcing) or 8 mA when the pin is low (sinking). This can differ between models, so check the datasheet of your model to verify.

74×74 Pinout

The 74×74 has 14 pins and contains two D flip-flop with set and reset laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
1RST	1	Input	Reset signal for the first the flip-flop (inverted).
1D	2	Input	Input to the first flip-flop.
1CLK	3	Input	Clock input to the first flip-flop.
1SET	4	Input	Preset signal for the first the flip-flop (inverted).
1Q	5	Output	Output from the first flip-flop.
1Q	6	Output	Output from the first flip-flop (inverted).
GND	7	Power	Connect to ground (GND).
2Q	8	Output	Output from the second flip-flop (inverted).
2Q	9	Output	Output from the second flip-flop.
2SET	10	Input	Preset signal for the second flip-flop (inverted).
2CLK	11	Input	Clock Input to the second flip-flop.
2D	12	Input	Input to the second flip-flop.
2RST	13	Input	Reset signal for the second the flip-flop (inverted).
VCC	14	Power	Positive power supply (VCC). Connect to +5V power.

Alternatives and Equivalents for 74HC74 / 74LS74

There are many versions of the 74×74 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:

• 74HC74 (High-speed CMOS)
• 74HCT74 (High-speed CMOS, TTL compatible)
• 74LS74 (High-speed TTL)
• 74LVC74 (Low Voltage TTL)
• 74AC74 (Advanced CMOS)
• 74ALS74 (Advanced Low-Power Schottky TTL)
• 74F74 (Very High Speed)
• 74C74 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC74 and SN74LS74 by Texas Instruments.

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

• CD4013 – Dual D flip-flop with preset and clear.
• 74×79 – Dual D flip-flop with asynchronous preset and clear.
• 74×171 – Quad D flip-flop with clear.
• 74×173 – Quad D flip-flop with asynchronous clear.
• 74×174 – Hex D flip-flop with common asynchronous clear.
• 74×175 – Quad D flip-flop with complementary outputs and asynchronous clear.

If you can’t find the 74×74 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 74LS74 and 74HC74 chips

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

• SN74HC74 (Texas Instruments)
• SN74LS74 (Texas Instruments)
• 74HC74 (Futurlec)
• 74LS74 (Futurlec)
• 74HC74/74HCT74 (Nexperia)
• 74HC74 (On Semconductor)