To Implement Logic Gates: NAND, AND, NOR, EX-OR, EX-NOR.

Aim

To Implement logic gates – NAND, AND, NOR, EX-OR, EX-NOR.

Apparatus Required:

Digital trainer kit, Logic gates IC, Connecting wires

Theory

Logic gates are electronic circuits which perform logical functions on one or more inputs to produce one output. There are seven logic gates. When all the input combinations of a logic gate are written in a series and their corresponding outputs written along them, then this input/output combination is called Truth Table. Various gates and their working are explained here.

AND gate

The AND gate produces a HIGH output when all of the inputs are HIGH. The abbreviation for this gate is AND & the operation is denoted by a dot (.). When any of the inputs are LOW, the output is LOW. The standard symbol for an AND gate is shown in figure below along with the associated Truth Table.

OR gate

The OR gate produces a HIGH output when any or all of the inputs is HIGH. The abbreviation for this gate is OR. When both inputs are LOW, the output is LOW. The standard symbol for an OR gate is shown in figure below along with the associated Truth Table. The operation function sign for the OR gate is (+)

NOT gate

NOT gate produces the complement of its input. This gate is also called an INVERTER. It always has one input and one output. Its output is LOW when input is HIGH and output is HIGH when input is LOW. The standard symbol for an NOT gate is shown in figure below along with the associated Truth Table. The operation function sign for the NOT gate is ( ‾ , ’ )

NOR gate

The NOR gate produces a HIGH output when all of the inputs are LOW. The abbreviation for this gate is NOR & the operation is same as OR followed with NOT. When any of the inputs are HIGH, the output is LOW. The standard symbol for an NOR gate is shown in figure below along with the associated Truth Table.

Exclusive OR (X-OR) Gate

The exclusive OR gate is a modified OR gate that produces a HIGH output, when number of 1’s at its inputs is odd, otherwise output is LOW. The standard symbol for an exclusive OR gate is shown in figure below along with the associated Truth Table.

Exclusive NOR (X-NOR) Gate

The exclusive NOR gate is a modified OR gate that produces a HIGH output, when number of 1’s at its inputs are even, otherwise output is LOW. The standard symbol for an exclusive NOR gate is shown in figure below along with the associated Truth Table.

Procedure:-

1. Place the breadboard gently on the observationtable.
2. Fix the IC which is under observation between the half shadow lineof breadboard, so there is no shortage ofvoltage.
3. Connect the wire to the main voltage source (Vcc) whose other end is connected to last pin of the IC (14 place from thenotch).
4. Connect the ground of IC (7th place from the notch) to the ground terminal provided on the digital labkit.
5. Give the input at any one of the gate of the ICs i.e. 1st, 2nd, 3rd, 4th gate by using connecting wires.(In accordance to ICprovided).
6. Connect output pins to the led on digital lab kit
7. Switch on the powersupply
8. If led glows then output is true, if it doesn’t glow output is false, which is numerically denoted as 1 and 0respectively.
9. Verify the truthtable.

Precautions:

1. All ICs should be checked before starting theexperiment.
2. All the connection should betight.
3. Always connect ground first and then connectVcc.
4. Suitable type wire should be used for different types ofcircuit
5. The kit should be off before changing theconnections.
6. after the completion of experiment, switch off the supply of theapparatus.

Result:Thus the truth tables for logic gates are verified.

Questions:

Q1:What is a logicgate?

Ans:Logic gate is a physical device implementing a Boolean function and performs Logical operation on one or more logic inputs and produces a single logic output.

Q2:What are universal gates?

Ans:NAND and NOR gates are called universal gates as any type of logic gates or logic Functions can be implemented by these gates.

Q3:What are basicgates?

Ans:AND, OR, Not are called basic gates.

Q4:When the output of a NOR gate is high?

Ans:If all the inputs arelow