13-05-2011, 04:03 PM
Name– study of universal building blocks – NAND gate and NOR gate.
Aim – to study the construction of basic gates using NAND gates and NOR gates.
Apparatus – IC 7400, IC 7402, circuit board, power supply +5V DC, LED, connecting wires, soldering iron, cutter etc.
Circuit diagrams
[attachment=13795]
[attachment=13796]
[attachment=13797]
Procedure –
1) You are given IC 7400 and IC 7402. Identify the ICs by reading their numbers and details from above given pin configurations.
2) Connect the gates with their respective pin numbers to construct the circuits of basic gates using NAND gates & NOR gates as shown in the circuit diagrams.
3) Connect final output of the circuit to the LED.
4) Verify the truth table for each theorem by giving different combinations of logic inputs as shown the respective truth tables.
5) Write the observed truth table of each theorem and hence, write the logic equation.
Brief theory –
1) NOT gate using NAND/NOR gates – here both input terminals of NAND/NOR gate are shorted together. So input signal at terminal A will be equally distributed to both inputs of the gate. Hence, the output will be the same as NOT gate with a single input. Thus, we have –
Y =
2) AND gate using NAND/NOR gates – when two NAND gates are cascaded we get one AND gate, as shown in the above left figure. Similarly when three NOR gates are connected as shown in the above right figure, we can obtain an AND gate.
Y = A.B
3) OR gate using NAND/NOR gates – when two NOR gates are cascaded we get one OR gate, as shown in the above right figure. Similarly when three NAND gates are connected as shown in the above left figure, we can obtain an OR gate.
Y = A + B
Observed truth tables –
Draw observed truth tables also on left page of practical record book.
Conclusion – in this way, we have studied that –
1) NAND gates can be used to produce any type of basic gate like AND gate, OR gate & NOT gate. Hence, NAND gate is called universal building block.
2) NOR gates can be used to produce any type of basic gate like AND gate, OR gate & NOT gate. Hence, NOR gate is also called universal building block.
