The output of an OR gate is connected to both inputs of a NAND gate. The combination serves as:
1
NOT gate
2
NOR gate
3
AND gate
4
OR gate
Official Solution
Correct Option: (2)
Step 1: OR gate output.
Output is A+B. Step 2: NAND with same inputs.
Y = (A+B)(A+B) = A+B Step 3: Conclusion.
This is NOR gate behaviour.
02
PYQ 2012
medium
physicsID: bitsat-2
An oscillator is nothing but an amplifier with:
1
positive feedback
2
negative feedback
3
large gain
4
no feedback
Official Solution
Correct Option: (1)
Step 1: Oscillator feedback.
An oscillator requires positive feedback to sustain its oscillations. Positive feedback amplifies the signal and reinforces the oscillations. Thus, the correct answer is (1).
03
PYQ 2013
medium
physicsID: bitsat-2
The circuit is equivalent to
1
AND gate
2
OR gate
3
Not gate
4
None of these
Official Solution
Correct Option: (2)
Step 1: Analyze the given circuit.
The circuit is a combination of logic gates. An OR gate produces a high output when any of its inputs are high. Step 2: Conclusion.
The given circuit functions as an OR gate. Final Answer:
04
PYQ 2014
medium
physicsID: bitsat-2
The combination of gates shown below yields:
1
OR gate
2
NOT gate
3
XOR gate
4
NAND gate
Official Solution
Correct Option: (3)
Step 1: The given combination is a standard XOR gate realization using NAND gates. Step 2: Output is high only when inputs are different.
05
PYQ 2015
medium
physicsID: bitsat-2
In a CE transistor amplifier, the audio signal voltage across the collector resistance of is . If the base resistance is and the current amplification of the transistor is , the input signal voltage is:
The combination of the gates shown in the following figure yields
1
NAND gate
2
OR gate
3
NOT gate
4
XOR gate
Official Solution
Correct Option: (2)
Step 1: Understanding the Concept
According to De Morgan's Laws, the combination of inverted inputs followed by a specific gate can be simplified into a single basic logic gate. Step 2: Key Formula or Approach
De Morgan's Theorem states:
1.
2. Step 3: Detailed Explanation
1. The inputs are first passed through NOT gates, giving and .
2. These are then fed into a NAND gate. The output of a NAND gate is the inversion of the product of its inputs:
3. Using De Morgan's Law ( ):
4. Since the double inversion cancels out ( ):
5. The expression represents an OR gate. Step 4: Final Answer
The combination yields an OR gate.
