or

Write the truth table of the OR gate and the NAND gate. How the OR gate is drawn by using the NAND gate?

Considering, 1 as high input/output and 0 as low input/output

OR Gate (Truth Table)

First  Input(A)Second Input(B)Output(Y)
111
101
011
000

NAND Gate (Truth Table)


First Input(A)Second Input(B)A.B(AND output)NAND Output(Y)
1110
0101
0001
1001


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As shown in the above figure, three NAND gates are connected such that the output of first two NAND gates are connected as inputs of the third NAND gate. The inputs for first two gates are combined to behave as a NOT gate. Therefore, these compliment outputs serve as input for the third NAND gate and an OR gate is obtained as shown by truth table of NAND gate.

TRUTH TABLE

First gate input(A)Second Gate Input(B)First Input of third gateSecond Input of Third GateOutput of third gate(Y)
00110
10011
01101
11001