The 74×09 (ex 74HC09) is a chip with four open-collector AND gates. This makes it simple to connect it to other chips that use different logic levels. But it also means you can’t use this chip as a direct replacement for a normal AND gate chip.
In this guide, you will learn all about this chip and how you can use its AND gates in your own circuit.
What does the 74HC09 / 74LS09 do?
The 74×09 gives you four basic open-collector AND gates that can be used 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:
How To Use This Chip
The 74HC09 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 74HC09 supports 2V to 6V, while the 74LS09 supports only 5V.
Once it has power connected, you can use any of the four AND gates inside.
This chip has open collector outputs. That means you can only sink current, not source it.
Each gate output of the 74HC09 can sink about 4 mA when powered with 5V. While the 74LS09 can usually sink about 8 mA of current. These values can vary between manufacturers of the chip though.
How To Use Open-Collector Outputs
The outputs from the 74HC09 are not your normal high/low outputs. Instead, they use something called open-collector. Open-collector outputs are outputs that are connected via a transistor. And the collector of the transistor is available at the pin. For an AND gate, it will look like this:
So when the output from the AND gate is ‘1’, it turns on the transistor that is connected to the output. When the output from the AND gate is ‘0’, it means the transistor will be off.
To turn on an LED when the AND gate output is ‘1’, you must connect the LED from your positive supply, via a resistor, to the open-collector output:
If you instead want to get your standard high/low output, you can get this by connecting a resistor from the output up to your positive supply. Then your output pin becomes a standard high/low output.
The advantage of using open-collector outputs is that you can choose your HIGH voltage level to make it compatible with whatever the voltage is of the next stage. The resistor acts as a pull-up resistor and makes the HIGH level approximately the same as the VCC voltage that you provide.
It’s important to notice that the output will be inverted: A logical HIGH from the AND gate turns the transistor ON so that the output voltage on the pin becomes low. A logical LOW leaves the transistor OFF so that the output voltage on the pin becomes HIGH.
The 74×09 has 14 pins and contains four open-collector AND gates laid out as shown in the pinout diagram below. Each gate has the open-collector symbol, to remind you of the type of output:
|1||Input||Input to the first AND gate.|
|2||Input||Input to the first AND gate.|
|3||Output||Open-collector output from the first 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||Output||Open-collector output from the fourth AND gate.|
|12||Input||Input to the fourth AND gate.|
|13||Input||Input to the fourth AND gate.|
|14||Power||Positive power supply (VCC). Connect to +5V power.|
74HC09 Circuit Example
Here’s a simple example circuit where an AND gate from the 74HC09 IC with 5V inputs is used with an ESP32 microcontroller that only supports 3.3V inputs:
To build this circuit, you’ll need the following parts:
- 1 x 74HC09
- 1 x 10 kΩ resistor
- ESP32 or another device that needs 3.3V
Alternatives and Equivalents for 74HC09 / 74LS09
There are many versions of the 74×09 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:
- 74HC09 (High-speed CMOS)
- 74HCT09 (High-speed CMOS, TTL compatible)
- 74LS09 (High-speed TTL)
- 74LVC09 (Low Voltage TTL)
- 74AC09 (Advanced CMOS)
- 74ALS09 (Advanced Low-Power Schottky TTL)
- 74F09 (Very High Speed)
- 74C09 (CMOS, similar to the 4000-series)
Some manufacturers also add a prefix, such as the SN74HC09 and SN74LS09 by Texas Instruments.
Can’t find the 74×09 anywhere? Then try one of the following IC alternatives:
- 74×08 – Quad 2-input AND gates (add a transistor to make it open-collector).
- 74×7001 – Quad 2-input AND gates (with Schmitt-trigger inputs).
- CD4081 – Quad 2-input AND gates (add a transistor to make it open-collector).
If you can’t find the 74×09 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 74LS09 and 74HC09 chips
Download the PDF datasheet for your version of the 74×09 here: