question_answer

The following truth table gives the output of a 2-input logic gate:       

A	B	Output
0	0	1
0	1	1
1	0	1
1	1	0

(i) Identify the logic gate used and draw its logic symbol. (ii) If the output of this gate is fed as input to a NOT gate, name the new logic gate so formed.                                      

Answer:

                    (i) The gate used is NAND gate. Its logic symbol is shown in Fig. (ii) When the output of NAND gate is fed to a NOT gate.

Input A	Input B	Output of NAND gate\[\Upsilon '=\overline{\text{A}\text{.B}}\]	Output of NOT gate \[\Upsilon =\overline{\Upsilon }'\].
0	0	1	0
0	1	1	0
1	0	1	0
1	1	0	1

    Clearly, output \[\Upsilon =A\,.\,B.\] So the new logic gate formed is an AND gate.