Introduction
The 74LS86 is a quad XOR (Exclusive-OR) gate IC. The XOR gate is a fundamental logic gate that outputs HIGH only when the inputs are different. If both inputs are the same (either both HIGH or both LOW), the output is LOW. In this experiment, we will explore how the XOR gate works using the 74LS86 IC.
Objective
The objective of this experiment is to demonstrate the behavior of the XOR gate by applying different input combinations and observing the corresponding output states using LEDs.
Components Needed
- 1 x 74LS86 XOR Gate IC
- 2 x Push Buttons (for input signals)
- 2 x Resistors (10kΩ for pull-down resistors)
- 1 x LED (for output indication)
- 1 x Resistor (220Ω for the LED)
- 1 x Breadboard
- Connecting Wires
- Power Supply (5V)
Circuit Diagram
Procedure
- Place the 74LS86 IC on the breadboard, and connect pin 7 (GND) to the ground rail and pin 14 (VCC) to the 5V power rail.
- Connect two push buttons to the input pins of one XOR gate (e.g., pins 1 and 2 for inputs A and B). These buttons will serve as the input signals.
- Connect two 10kΩ resistors between the input pins (pins 1 and 2) and ground as pull-down resistors to ensure clean LOW signals when the buttons are not pressed.
- Connect the output pin of the XOR gate (e.g., pin 3 for the output of the gate) to the anode of the LED.
- Connect the cathode of the LED to ground through a 220Ω resistor.
- Power the circuit by applying 5V to the IC, and observe the LED behavior:
- When both buttons are not pressed (inputs are LOW), the output is LOW, and the LED will be off.
- When one button is pressed (one input HIGH and one input LOW), the output is HIGH, and the LED will turn on.
- When both buttons are pressed (both inputs HIGH), the output is LOW, and the LED will be off again.
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Results
The LED will light up only when the two inputs to the XOR gate are different (one HIGH and one LOW). When both inputs are the same (either both HIGH or both LOW), the LED remains off. This confirms the behavior of the XOR gate as described by its truth table.
Conclusion
In this experiment, we demonstrated the operation of the 74LS86 XOR gate. XOR gates are commonly used in digital circuits, especially in arithmetic and error detection applications, where the comparison of signals is essential. The XOR gate outputs HIGH when the inputs differ, which is useful in numerous logic circuit designs.
