The CD4077 is a CMOS chip with four XNOR gates. Because each gate has two inputs and it has four gates inside, it’s usually called a Quad 2-Input XNOR Gate.
An XNOR gate is basically an XOR gate with a NOT gate on the output: It gives a HIGH output whenever its two inputs are equal. If the inputs are both HIGH or both LOW, then the output will be HIGH, otherwise LOW.
Pin Overview
| Pin Name | Pin # | Type | Description |
|---|---|---|---|
| VDD | 14 | Power | Supply Voltage (+3 to +15V) |
| GND | 7 | Power | Ground (0V) |
| A1 to A4 | 1, 5, 8, 12 | Input | Inputs A of the four XNOR gates |
| B1 to B4 | 2, 6, 9, 13 | Input | Inputs B of the four XNOR gates |
| Q1 to Q4 | 3, 4, 10, 11 | Output | Outputs from the four XNOR gates |
What is an XNOR gate?
An XNOR gate is a logic gate that works like an XOR gate with a NOT gate on the output. So it gives the exact opposite output compared to an XOR.
The XNOR gives a HIGH output whenever its inputs are the same. So if both inputs are HIGH, or if both inputs are LOW, the output will be HIGH.
Check the truth table below to see what the value will be for any two inputs:
| Input A | Input B | Output Q |
|---|---|---|
| 0 | 0 | 1 |
| 1 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 1 | 1 |
How To Use the CD4077?
For any IC in the 4000 series, you need a power supply voltage of 3 to 15V. Some versions of the chip support up to 20V. Check the datasheet of your version of the chip for exact values.
You need to connect the VDD pin to the positive supply terminal and the GND pin to the negative supply terminal. Then you can use any of the XNOR gates in the chip.
The A and B pins are the inputs to the four XNOR gates in the IC.
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The Q pins are the outputs from the XNOR gates.
CD4077 Example Circuit – Edge Detection Circuit
This circuit detects a signal going from low to high, or from high to low, and converts it to a pulse that keeps an LED on for a short while. No matter if the input pulse is long or short, the LED will stay on for the same amount of time.
To build this you’ll need:
- An LED (D1)
- A chip with XNOR gates such as the CD4077BE
- 100 kΩ resistor (R1)
- 1 kΩ resistor (R2)
- 100 µF Capacitor (C1)
Alternatives and Equivalents for CD4077
You likely find the 4077 IC marked as CD4077, NTE4077, MC14077, HCF4077, TC4077, or HEF4077. Usually with a few extra characters at the end (Ex: CD4077BE).
This has to do with the manufacturer of the chip and the technology used. But the functionality and the pins are the same.
If they don’t have any of these chips in your local electronics store, check out my list of online stores where you can find components and tools for all your electronics projects.
Can’t find the 4077? Then try one of the following IC alternatives with 2-input XNOR gates:
- 74HC7266: Quad 2-input XNOR
- 74HC266: Quad 2-input XNOR (open collector outputs)
- 74HC810/811: Quad 2-input XNOR
4077 Datasheet
Download the PDF datasheet for the IC 4077 here:
CD4077B (Texas Instruments)
HEF4077B (Nexperia)
Go back to the full overview of the 4000-series integrated circuits
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