Semiconductor Electronics · Question 30

In the digital circuit shown in the figure, for the given inputs the P and Q values are : [figure]

1. P = 0, Q = 1
2. P = 1, Q = 0
3. P = 0, Q = 0
4. P = 1, Q = 1

Answer

(3) P = 0, Q = 0

Solution

Both inputs are 1.

NAND gate: 1 1 = 0

The two NOT gates (each fed with 1) give 0 and 0

OR gate: 0 + 0 = 0

AND gate (inputs: NAND output 0 and OR output 0): P = 0 0 = 0

NOT gate after NAND: 0 = 1

NOR gate (inputs 1 and OR output 0): Q = 1 + 0 = 0

P = 0, Q = 0

Answer: (3)