For the following figure:
what is the ouput if
a) both inputs are low
b) if one input is high and one low
c) does the circuit act like an OR or AND gate
I understand that the output for the first part of the circuit is 1 if both inputs are low only. I am confused about the connection between the first and second part of the circuit.
By low, I assume you mean zero ? A nor gate gives one when both inputs are zero & gives zero in the 3 other possible cases. So the answer to a) is high & b)is low. The output from the first NOR gate will be $A$ NOR $B$, this will then be the inputs for both sides of the next NOR gate & so a formula for Y is given by \begin{eqnarray*} Y = (A \ NOR\ B) \ NOR\ (A \ NOR\ B) \end{eqnarray*} Now make a truth table for this & you will be able to rapidly conclude that it is the same as an OR gate.