Question

When all the inputs of a NAND gate are connected together, the resulting circuit is a:
A) NOT gate
B) An AND gate
C) An OR gate
D) NOR gate

Answer 1

Hint: It is incredibly useful for the NAND (non-and) gate to be a universal gate for electronics since it can build any logic circuit using only NAND gates, simple or complex. You can store on integrated circuits that contain NAND gates only and make sure even the most complicated circuits can be designed with your NAND port stock when you start designing your own digital circuits.

Complete step by step solution:
NOT Gate: You may simply connect the two inputs in the NAND gate together to create a NOT Gate from the NAND Gate. Since the two inputs of the NAND gate are connected, only two input combinations can be used. The NAND Gate will emit a LOW if any input is HIGH. The NAND gate would be output HIGH if all inputs are LOW. The circuit then works much like a NOT gate.

AND Gate: Using two NAND gates to build an AND gate. The first NAND port does what NAND Gates are doing: LOW returns if the inputs are HIGH and HIGH if the two inputs do otherwise. Then the second NAND gate is set up to invert the output from the first NAND gate as a NOT gate.

OR Gate: To build a OR gate you need three NAND gates. First you use a NAND gate pair setup to invert both inputs as NOT gates. The third NAND gate then creates a LOW output if all initial inputs are lower. The third gate's output is HIGH when one of the original inputs is HIGH, or if all the original inputs are HIGH.

NOR Gate: To construct a NOR gate, it takes four NAND gates. This circuit is identical to the OR gate circuit, with a NOT gate added to invert the output from the third NAND gate. Inverting the output changes the overall function of the circuit from OR to NOR.

Hence option (A) is correct.

Note: All other gates, namely OR, NOT and XOR may be derived from it. NAND and NOR are considered universal gates. Even though and, or not simple gates, any of its features can be extracted using nand and not so. Another significant feature can be translated to Nand or nor because of this AOI logic.