Understand how basic logic gates (AND, OR, NOT, NAND, NOR, etc.) work.
Create and verify truth tables for these logic gates.
Build and test circuits using a digital trainer and IC components.
Breadboard
Digital trainer equipped with integrated switches and LEDs
Connecting wires and jumper cables
IC components:
AND Gate: 74LS08
OR Gate: 74LS32
NOT Gate: 74LS04
NAND Gate: 74LS00
NOR Gate: 74LS02
Manufacturer datasheets for each IC component
Logic gates are the basic building blocks of digital circuits. They perform Boolean operations that are the foundation of computers working. Each logic gate has specific rules that connect its inputs, A and B, to its output, F. Some gates can handle multiple inputs to perform more complex tasks. In this lab exercise, you will learn how logic gates work by building electric circuits and verify their truth tables. Following are the truth tables and symbols of common logic gates:
Download datasheet from internet for the given chip.
Construct circuit following the datasheet for the given AND, OR, NOT, NAND, NOR, XOR or XNOR gates using breadboard and digital trainer.
Record the outputs for all possible input combinations.
Verify that the truth tables matches theoretical expectations.
The experiment involves performing logic gate operations using IC chips like 74LS00, 74LS02 on a breadboard connected to a digital trainer. Follow these steps carefully:
● Handle ICs with care: Always discharge static electricity by touching a grounded object before handling the ICs to avoid electrostatic discharge (ESD) damage.
● Ensure that no IC pin gets damaged while inserting it into the breadboard and also while removing it from the breadboard.
● Ensure the working area, digital trainer and breadboard are in a clutter free area.
● Follow IC datasheet for pin configuration and functionality.
● Insert the IC into the breadboard across the center groove to ensure no short circuits occur between pins.
● Connect pin 7 to GND and pin 14 to +5V for powering the IC. Use jumpers to connect the IC pins to the power rails of the breadboard.
● Use the digital trainer's switches as input signals. Connect the inputs (A, B, etc.) to the respective pins of the IC as specified in the datasheet.
● Connect the output pin of the IC to an LED on the digital trainer to observe the results.
● Use the digital trainer's 5V supply to power the breadboard. Confirm proper power connections before turning on the supply.
● Toggle the switches on the digital trainer to set different input combinations.
● Observe the corresponding output on the LEDs.
● Record the truth table for each gate operation and verify it against theoretical results.
● After testing one logic gate IC, turn off the power supply, carefully remove the IC, and insert the next IC for the subsequent logic gate operation.
● Repeat the connections and testing steps for each IC.
● Turn off the power supply and disconnect all jumpers.
● Return the ICs to the instructor for use in next lab.
● Avoid Short Circuits: Double-check connections before turning on the power supply.
● Use Correct Pins: Refer to the datasheet for accurate pin mapping. Incorrect connections can damage the IC.
● Power Off During Changes: Always turn off the power supply when inserting or removing ICs to prevent damage.
● Secure Connections: Ensure jumpers are firmly connected to the correct breadboard terminals.
Design a circuit using AND, OR and NOT gates to implement XOR gate.
Practical Challenge: Implement a half-adder circuit using AND and XOR gates. Verify its addition operation (Sum and Carry).
● Record all truth tables and compare them to theoretical results.
● Identify and correct any discrepancies.
● Why are NAND and NOR gates considered universal gates?
● How can you design a NOT gate using a NAND gate?
● How can you design an OR gate using only the NAND gates?
● How can you design an AND gate using only the NAND gates?
Summarize the key takeaways, such as the functionality of each gate, their truth tables, and how they can be combined to perform advanced computations.
Students will understand the operation of logic gates.
They will learn to construct truth tables and compare theoretical vs. practical results.
By combining gates, students will gain experience designing basic digital circuits.