# Find the truth table for the circuit shown in the figure. What logic function will the circuit perform if the constant +5 V input to the first two gates is changed to ground potential?

Solution :

a. Truth table for the given circuit of logic function:

Y = $$[\overline{\overline{5V.V_{A}}.\overline{5V.V_{B}}}]$$

Y = VA + VB

Y = OR operation

Inputs(V)

 VA VB +5V 0 0 5 5 0 5 0 5 +5 +5 +5 +5
Intermediate(V)

 5V.VA 5V.VB $$\overline{5V.V_{A}}$$ $$\overline{5V.V_{B}}$$ 0 0 5 5 0 5 0 5 +5 +5 0 0 0 5 0 5
Output(V)

 $$\overline{\overline{5V.V_{A}}.\overline{5V.V_{B}}}$$ 0 5 5 5