NAND and NOR are only universal gates? - mbits-mirafra/digitalDesignCourse GitHub Wiki

This page gives extensive knowledge of why basic gates are not called universal gates

**Consider AND gate and let us try to implement NOT gate

When A=0 the both inputs will be zero and when both inputs are zero of an AND gate the output is zero but the expected output was 1(as we tired implementing Not gate).

AND gate can be A Buffer but not an Inverter.

So AND gate cannot be an Universal gate.

**Consider OR gate and let us try to implement NOT gate

When A=0 the both inputs will be zero and when both inputs are zero of an OR gate the output is zero but the expected output was 1(as we tired implementing Not gate).

When A=1 the both inputs will be high and when both inputs are high of an OR gate the output is 1 but the expected output was 0(as we tired implementing Not gate).

So we can not implement NOT gate using OR gate.

**Consider EXOR gate when both the inputs are same Output will be Zero.

**In EXNOR gate when both the inputs are same Output will be High .

**Consider NAND gate and try to implement not gate

When A=0 the both inputs will be zero and when both inputs are zero of an NAND gate the output is 1 , it is same as the expected output(as we tired implementing Not gate).

When A=1 the both inputs will be 1 and when both inputs are 1 of an NAND gate the output is 0 , it is same as the expected output(as we tired implementing Not gate).

**As we can not implement NOT gate using any other gates except NAND and NOR gate they are called the universal gates.