Physics Class 12 NCERT Solutions: Chapter 14 Semiconductor Electronics Materials Devices and Simple Circuits Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Basic Logic Gates

Q: 15. You are given the two circuits as shown in figure. Show that circuit (a) acts as OR gate while the circuit (B) acts as AND gate.

Q_15_Circuit of or Gate and and Gate

(A) A and B are the inputs and is the output of the given circuit. The left half of the given figure acts as the NOR Gate, while the right half acts as the NOT Gate. This is shown in the following figure.

Q_15_A_CIrcuit of Half-Nor Gate Ang Half NOT Gate

Hence, the output of the NOR Gate

This will be the input for the Not Gate. Its output will be

Hence, this circuit functions as an OR Gate.

(B) A and B are the inputs and Y is the output of the given circuit. It can be observed from the following figure that the input that the inputs of the right half NOR Gate are the outputs of the two NOT Gates.

Q_15_B_Circuit of theRightHalfNORGatearethe Outputsofthe

Hence, the output of the given circuit can be written as:

Hence, this circuit functions as an AND Gate.

Q: 16. Write the truth table for a NAND gate connected as given in Figure.

Q_16_Circuit of the NAND Gate

Hence identify the exact logic operation carried out by this circuit.

Answer:

A acts as the two inputs of the NAND gate and Y is the output, as shown in the following figure.

Q_16_1_Circuit of the NAND Gate

The truth table for equation (i) can be drawn as:

Q_16_2_Truth Table for NAND Gate
A
0
1

This circuit functions as a NOT gate. The symbol for this logic circuit is shown as:

Q_16_3_Circuit of the NOT Gate

Q: 17. You are given two circuits as shown in figure, which consist of NAND gates. Identify the logic operation carried out by the two circuits.

Q_17_NAND Gate for Identify the Logic Operation of …

Answer:

In both the given circuits, A and B are the inputs and Y is the output.

(A) The output of the left NAND gate will be . As shown in the following figure.

Q_17_A_The Output of the Combination of the Two NAND Gates

Hence, the output of the combination of the two NAND gates is given as:

Hence, this circuit functions as an AND gate.

(B) is the output of the upper left of the NAND gate and is the output of the lower half of the NAND gate, as shown in the following figure.

Q_17_B_The Output of the Upper Left of the NAND Gate and Low …

Hence, the output of the combination of the NAND gates will be given as:

Hence, this circuit functions as an OR gate.