Question

In the circuit, the logical value of A = 1 or B = 1 when potential at A or B is 5 V and the logical value of A = 0 or B = 0 when potential at A or B is 0 V. The truth table of the given circuit will be:

• A. A B Y
  0 0 0
  1 0 0
  0 1 0
  1 1 1
• B. A B Y
  0 0 0
  1 0 1
  0 1 1
  1 1 1
• C. A B Y
  0 0 0
  1 0 0
  0 1 0
  1 1 0
• D. A B Y
  0 0 1
  1 0 1
  0 1 1
  1 1 0

Answer 1

Answer: (A)

A B Y
0 0 0
1 0 0
0 1 0
1 1 1

Answer 2

The correct answer is (A) :
A B Y
0 0 0
1 0 0
0 1 0
1 1 1
When both A and B have logical value ‘1’ both diode are reverse bias and current will flow in resistor hence output will be 5 volt i.e. logical value ‘1’.
In all other case conduction will take place, hence output will be zero volt i.e. logical value ‘0’.
So, the given circuit is equivalent to an AND gate.
∴ A B Y
0 0 0
0 1 0
1 0 0
1 1 1