7400 Series Guide: 74HC73/74LS73 (Dual J-K flip-flop)

The 74×73 (ex 74HC73) is a chip with two negative-edge-triggered J-K flip-flops.

In this guide, you’ll learn the things you need to know about this chip in order to use JK flip-flops in your own projects.

What does the 74HC73 / 74LS73 do?

The 74×73 gives you two J-K flip-flops with reset that you can use individually. This is a type of flip-flop that can be set, reset, and toggled. It can be used for making counters, event detectors, frequency dividers, and much more.

In the table below, you can see how to set, reset, and toggle the flip flop output.

Clk	J	K	Q	Description
0	X	X	Q	Memory (no change)
1	0	0	Q	Memory (no change)
0	1	0	1	Set
0	0	1	0	Reset
0	1	1	Q̅	Toggle

How To Use This Chip

The 74HC73 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 74HC73 supports 2V to 6V, while the 74LS73 only supports 5V.

The HC version of this chip can supply a maximum of 25 mA from its output pin.

If you’re using the LS 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).

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 any of the two positive-edge-triggered J-K flip-flop with reset inside.

74×73 Pinout

The 74×73 has 14 pins and contains two negative-edge-triggered J-K flip-flop with reset laid out as shown in the pinout diagram below:

Pin Name	Pin #	Type	Description
CLK1	1	Input	Input to the first flip-flop (negative-edge triggered).
RST1	2	Input	Control signal that controls the flip-flop (inverted).
K1	3	Input	Input to the flip-flop.
VCC	4	Power	Positive power supply (VCC). Connect to +5V power.
CLK2	5	Input	Input to the second flip-flop (negative-edge triggered).
RST2	6	Input	Control signal that controls the flip-flop (inverted).
J2	7	Input	Input to the flip-flop.
Q2	8	Output	Output from the second flip-flop (inverted).
Q2	9	Output	Output from the second flip-flop.
K2	10	Input	Input to the flip-flop.
GND	11	Power	Connect to ground (GND).
Q1	12	Output	Output from the first flip-flop.
Q1	13	Output	Output from the first flip-flop (inverted).
J1	14	Input	Input to the flip-flop.

Alternatives and Equivalents for 74HC73 / 74LS73

There are many versions of the 74×73 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:

• 74HC73 (High-speed CMOS)
• 74HCT73 (High-speed CMOS, TTL compatible)
• 74LS73 (High-speed TTL)
• 74LVC73 (Low Voltage TTL)
• 74AC73 (Advanced CMOS)
• 74ALS73 (Advanced Low-Power Schottky TTL)
• 74F73 (Very High Speed)
• 74C73 (CMOS, similar to the 4000-series)

Some manufacturers also add a prefix, such as the SN74HC73 and SN74LS73 by Texas Instruments.

Can’t find the 74×73 anywhere? Then try one of the following IC alternatives:

• 74×67 – AND-gated master-slave J-K flip-flop.
• 74×70 – AND-gated positive-edge triggered J-K flip-flop.
• 74×72 – AND-gated master-slave J-K flip-flop.
• 74×76 – Dual J-K flip-flop.
• 74×78 – Dual negative-edge triggered J-K flip-flop.
• 74×107 – Dual negative-edge triggered J-K flip-flop.
• 74×109 – Dual J-K flip-flop.
• 74×112 – Dual negative-edge-triggered J-K flip-flop.
• 74×113 – Dual negative-edge-triggered J-K flip-flop.
• 74×114 – Dual J-K flip-flop.
• CD4027 – Dual J-K master-slave flip-flop.
• CD4095 – Gated J-K flip-flop.
• CD4096 – Gated J-K flip-flop.

If you can’t find the 74×73 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 74LS73 and 74HC73 chips

Download the PDF datasheet for your version of the 74×73 here:

• 74LS73 (Futurlec)
• 74HC73 (Nexperia)
• SN74HCT73 (Texas Instruments)
• SN74LS74 (Texas Instruments)