PUC Karnataka Science Class 12Department of Pre-University Education, Karnataka
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# Write the Truth Table for Circuit Given in Fig. 14.47 Below Consisting of Nor Gates and Identify the Logic Operation (Or, And, Not) Which this Circuit is Performing. - PUC Karnataka Science Class 12 - Physics

#### Question

Write the truth table for circuit given in Fig. 14.47 below consisting of NOR gates and identify the logic operation (OR, AND, NOT) which this circuit is performing. (Hint: A = 0, B = 1 then A and B inputs of second NOR gate will be 0 and hence Y=1. Similarly work out the values of Y for other combinations of A and B. Compare with the truth table of OR, AND, NOT gates and find the correct one.)

#### Solution

A and B are the inputs of the given circuit. The output of the first NOR gate is bar(A +B). It can be observed from the following figure that the inputs of the second NOR gate become the out put of the first one. Hence, the output of the combination is given as:

Y = bar(bar(A+B) + bar(A+B)) = bar(bar(A).bar(B)) + bar(barA.barB)

= bar(barA.barB) = bar(barA) + bar(barB) = A+ B

The truth table for this operation is given as:

 A B Y (=A + B) 0 0 0 0 1 1 1 0 1 1 1 1

This is the truth table of an OR gate. Hence, this circuit functions as an OR gate.

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#### APPEARS IN

NCERT Solution for Physics Textbook for Class 12 (2018 to Current)
Chapter 14: Semiconductor Electronics: Materials, Devices and Simple Circuits
Q: 18 | Page no. 511

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Solution Write the Truth Table for Circuit Given in Fig. 14.47 Below Consisting of Nor Gates and Identify the Logic Operation (Or, And, Not) Which this Circuit is Performing. Concept: Digital Electronics and Logic Gates.
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