The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of this combination of gates and write its truth table.
Solution
The OR gate gives Y′=A+B. Both inputs of the NAND gate are tied to Y′, so
Y=Y′⋅Y′=Y′=A+B.
This is the NOR operation; the truth table is 00→1,01→0,10→0,11→0. Y=A+B(NOR)