Objective

The objective of this experiment is to explore the logic functionality of the 74LS00 NAND gate and how it can be used to perform basic digital logic operations like AND, OR, and NOT gates by wiring NAND gates together.

Components Needed

• 1 x 74LS00 NAND Gate IC
• 2 x Pushbutton Switches (for inputs)
• 1 x LED (for output)
• 1 x Resistor (220Ω for LED)
• 2 x Resistors (10kΩ for pull-down resistors)
• 1 x Breadboard
• Connecting Wires
• Power Supply (5V)

Circuit Diagram

Procedure

1. Place the 74LS00 IC on the breadboard.
2. Connect pin 14 (VCC) to 5V and pin 7 (GND) to ground.

Step 1: NAND Gate Logic Test

3. Choose one NAND gate (e.g., gate 1 with inputs at pins 1 and 2, output at pin 3).
4. Connect two pushbuttons to pins 1 and 2 as inputs, using pull-down resistors (10kΩ) from the input pins to ground to ensure a defined low state.
5. Connect the output pin (pin 3) to the anode of the LED, and connect the cathode of the LED to ground through a 220Ω resistor.
6. Power the circuit and press the pushbuttons to test the NAND gate behavior:
   • If both inputs are HIGH (logic 1), the output will be LOW (LED off).
   • If either or both inputs are LOW (logic 0), the output will be HIGH (LED on).

Step 2: Using NAND Gates to Build Other Logic Gates

Now, we will use the NAND gates to build other basic logic gates like AND, OR, and NOT.

Building an AND Gate with NAND Gates

7. To create an AND gate, connect the output of a NAND gate (pins 3) to both inputs of another NAND gate (e.g., pin 4 and pin 5 of gate 2).
8. The output of the second NAND gate (pin 6) will behave like an AND gate, where:
   • If both inputs are HIGH, the output is HIGH (LED on).
   • If either or both inputs are LOW, the output is LOW (LED off).

Building an OR Gate with NAND Gates

9. To create an OR gate, you will need three NAND gates:
   • Use two NAND gates (gate 1 and gate 2) as inverters for each input.
   • Feed the outputs of these two NAND gates into the inputs of a third NAND gate.
   • The final output will behave like an OR gate.

Building a NOT Gate with a Single NAND Gate

10. As explained earlier, connecting both inputs of a NAND gate together creates a NOT gate (inverter). Use this configuration to invert any input signal.