7400 Series Guide: 74HC107/74LS107 (Dual J-K flip-flops)

The 74×107 (ex 74LS107) is a chip that has two J-K negative-edge-triggered flip-flops. A useful chip for for digital circuits that require memory, state retention, and toggling functionality.

In this guide, you’ll explore the working principles, pin configuration, and practical applications of the 74×107, so that you can use this flip-flop in your own electronic projects.

What does the 74LS107 do?

The 74×107 contains two independent J-K flip-flops that are particularly known for their toggle feature.

Each flip-flop in the 74×107 has J, K, clock, clear and complementary outputs. The J-K flip-flop is used to store binary data and are also capable of performing various functions such as memory storage, counters, and toggle switches depending on the input signals provided.

Here is a brief outline of its function:

• J and K Inputs: Control inputs that determine the action taken with each clock pulse.
• Clear (CLR): An asynchronous input which, when activated, resets the flip-flop output to zero regardless of other inputs.
• Clock (CLK): Edge-triggered; reacts on the negative-going edge of the clock signal.

The 74×107 is commonly used in applications requiring toggle operations, binary counting, and other sequential logic operations.

How To Use This Chip

The 74LS107 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 74HC107 supports 2V to 6V, while the 74LS107 only supports 5V.

Once you’ve connected it to power, you can use any of the two J-K flip-flops inside.

Output Current

The 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.

Pinout

The 74×107 has 14 pins and contains two negative-edge-triggered J-K flip-flops with reset laid out as shown in the pinout diagram below:

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

Alternatives and Equivalents for 74HC107 / 74LS107

There are many versions of the 74×107 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:

• 74HC107 (High-speed CMOS)
• 74HCT107 (High-speed CMOS, TTL compatible)
• 74LS107 (High-speed TTL)
• 74LVC107 (Low Voltage TTL)
• 74AC107 (Advanced CMOS)
• 74ALS107 (Advanced Low-Power Schottky TTL)
• 74F107 (Very High Speed)
• 74C107 (CMOS, similar to the 4000-series)
• 74107 and 74S107

Some manufacturers also add a prefix, such as the SN74LS107 by Texas Instruments.

Can’t find the 74×107 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.
• 74×73 – Dual positive-edge triggered J-K flip-flop.
• 74×76 – Dual J-K flip-flop.
• 74×78 – 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 74×107 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 and chips

Download the PDF datasheet for your version of the 74×107 here:

• 74HC107 (Nexperia)
• CD74HC107 (Texas Instruments)
• SN74LS107 (Texas Instruments)
• 74LS107 (National Semiconductor)