Which logic gate is represented by the following combination of logic gates?
1
OR
2
NAND
3
AND
4
NOR
Official Solution
Correct Option: (3)
In the given logic gate diagram:
- Two NOT gates are applied to the inputs.
- Their outputs are fed into an OR gate. This configuration corresponds to:
Using De Morgan’s theorem:
Taking the complement again (which is not shown here, so this is the output itself), this is equivalent to the NAND operation inverted, hence it's:
So, the final result is , which is the output of an AND gate.
02
PYQ 2025
medium
physicsID: upcatet-
NAND gate means
1
Inversion followed by AND gates
2
AND gates followed by an inverter
3
AND gate followed by OR gate
4
None of these
Official Solution
Correct Option: (2)
A NAND gate is a combination of an AND gate followed by a NOT gate (inverter). The NAND (Not AND) gate gives an output that is the inverse of the output of an AND gate. Mathematically:
So, first the inputs are passed through an AND gate and the result is then inverted.
03
PYQ 2025
medium
physicsID: upcatet-
The output of the two-input OR gate is high
1
Only if both inputs are high
2
Only if both inputs are low
3
Only if one input is high and the other is low
4
If at least one of the inputs is high
Official Solution
Correct Option: (4)
An OR gate gives a high output (logic 1) if any one or both of its inputs are high. The only time an OR gate outputs low (logic 0) is when both inputs are low. Truth table for a two-input OR gate:
