IC 74266 – Quad 2-Input Exclusive-NOR (XNOR) Gate with Open-Collector Outputs

Overview

The IC 74266 – Quad 2-Input Exclusive-NOR (XNOR) Gate is a member of the 74xx TTL logic series, designed as a quad 2-input Exclusive-NOR (XNOR) gate with open-collector outputs. This IC contains four independent XNOR gates, each of which performs the logical XNOR operation on two input signals. The XNOR gate outputs a HIGH (1) only when both inputs are equal (either both HIGH or both LOW). The open-collector outputs require an external pull-up resistor and are capable of sinking current, making them ideal for wired-AND logic and interfacing with different logic levels.

Features

• Quad 2-Input XNOR Gates: Includes four independent XNOR gates in one package, each with two inputs.
• Open-Collector Outputs: Requires external pull-up resistors and allows for wired-AND configurations.
• TTL Compatible: Standard TTL voltage levels make it easy to interface with other TTL logic circuits.
• Wide Operating Voltage: Typically operates at 5V, standard for TTL devices.
• Low Power Consumption: Efficient in terms of power usage, suitable for various digital applications.

Pin Configuration

The IC 74266 is typically available in a 14-pin Dual In-line Package (DIP) with the following pin configuration:

• Pins 1, 4, 9, 12: Inputs (A1, A2, A3, A4) for the four XNOR gates.
• Pins 2, 5, 10, 13: Inputs (B1, B2, B3, B4) for the four XNOR gates.
• Pins 3, 6, 11, 14: Outputs (Y1, Y2, Y3, Y4) of the XNOR gates.
• Pin 7: Ground (GND).
• Pin 14: Positive Supply Voltage (Vcc).

Working Principle

The IC 74266 – Quad 2-Input Exclusive-NOR (XNOR) Gate follows the logical XNOR operation, where the output is HIGH when both inputs are equal:

1. Logical XNOR Function: The XNOR gate outputs a HIGH (1) when both inputs are the same:
   • Input A = 0, Input B = 0 → Output Y = 1
   • Input A = 1, Input B = 1 → Output Y = 1
   • Input A = 0, Input B = 1 → Output Y = 0
   • Input A = 1, Input B = 0 → Output Y = 0
2. Open-Collector Outputs: The open-collector outputs allow for multiple outputs to be tied together to create a wired-AND logic configuration. An external pull-up resistor is required to pull the output to a HIGH state when not sinking current.

Applications

• Digital Comparison: Used in circuits where the equality of two binary signals needs to be checked.
• Error Detection: Employed in parity checkers and other error-detection systems.
• Wired-AND Logic: Useful in applications where multiple outputs need to be combined in a wired-AND configuration.
• Interfacing: Suitable for interfacing between different logic levels due to open-collector outputs.

Example Circuit

• Parity Checker: In a digital communication system, the IC 74266 can be used to check the parity of transmitted data. If the parity bit matches the calculated parity, the output of the XNOR gate will be HIGH, indicating no error.

Advantages

• Multiple XNOR Gates: Provides four XNOR gates in a single package, reducing circuit complexity.
• Versatile Output Configuration: Open-collector outputs allow for flexible logic design and interfacing.
• Reliable Performance: Stable operation in digital circuits, suitable for various logic applications.

Conclusion

The IC 74266 – Quad 2-Input Exclusive-NOR (XNOR) Gate is a versatile logic gate IC, offering four independent 2-input XNOR gates with open-collector outputs. Its ability to perform logical XNOR operations and provide flexible output configurations makes it a valuable component in digital electronics. Whether you’re designing error-detection systems, digital comparators, or wired-AND logic circuits, the IC 74266 provides the functionality and reliability needed for high-performance applications.