Introduction
The 74LS08 IC contains four independent AND gates. AND gates are basic logic gates that output a HIGH signal (1) only if all of their inputs are HIGH. This experiment demonstrates how the 74LS08 AND gate works in a simple logic circuit.
Objective
The objective of this experiment is to create a logic circuit using the 74LS08 AND gate and test the truth table of the gate by manipulating the inputs and observing the output behavior.
Components Needed
- 1 x 74LS08 AND Gate IC
- 2 x Push Button Switches
- 1 x LED
- 1 x Resistor (220Ω for LED)
- 2 x Resistors (10kΩ for pull-down on push buttons)
- 1 x Breadboard
- Connecting Wires
- Power Supply (5V)
Circuit Diagram
Procedure
- Place the 74LS08 IC on the breadboard.
- Connect pin 14 (VCC) to the positive 5V power supply and pin 7 (GND) to ground.
- Connect two push button switches to act as inputs to the AND gate. Connect one side of each button to the 5V supply and the other side to the inputs of the AND gate.
- Add 10kΩ pull-down resistors between the ground and the inputs of the AND gate to ensure a defined LOW state when the buttons are not pressed.
- Connect the output of the AND gate (for example, using the first AND gate: pins 1 and 2 for inputs, and pin 3 for output) to the anode of an LED.
- Connect the cathode of the LED to ground through a 220Ω current-limiting resistor.
- Power the circuit with 5V. The LED should only turn on when both input buttons are pressed, demonstrating the behavior of the AND gate.
Step 1: Input Configuration
Step 2: Output Configuration
Step 3: Testing the Circuit
No Ads Available.
Results
The LED will turn on only when both push buttons are pressed simultaneously, confirming that the 74LS08 AND gate works according to the truth table of an AND gate. The LED remains off if either one or both buttons are not pressed.
Truth Table
| Input A | Input B | Output (LED) |
|---|---|---|
| LOW (0) | LOW (0) | LOW (0) |
| LOW (0) | HIGH (1) | LOW (0) |
| HIGH (1) | LOW (0) | LOW (0) |
| HIGH (1) | HIGH (1) | HIGH (1) |
Conclusion
In this experiment, we successfully used the 74LS08 AND gate to create a simple logic circuit. The AND gate operates according to its truth table, where the output is HIGH only when both inputs are HIGH. This basic understanding of the AND gate can be applied to more complex logic designs.
