﻿ Two ways to implement inverter from universal NAND gate
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Getting through interviews is always a challenging task and requires thorough preparation . Here is a list of probable questions that may appear in an interview related to RTL skills.

Digital Interview Questions

Give two ways to convert a two input NAND gate to an inverter

Lets first look at the NAND truth Table below

First Method is connect the 1 bit input to either 'a' or 'b' and connect other to always ‘1’. Detailed discussion below:-

So for the first method there can be two possible combinations.

First combination:-

For Row’s 3 and 4 Input A is always ‘1’

When Input B = 1 then the output is b= 0.

When Input B = 0 then the output is b=1.

Hence a functionality of an inverter.

Second combination:-

Row 2 and 4 in above table have Input A tied to 0. The polarity of B input is inverted at output.

Second Method : Apply same inputs to a and b

From table above we have  in rows 1 and 4 following polarities.

Input a and b = 0 and output = 1

Input a and b = 1 and output = 0

So when both the inputs are tied together, we get an inverter.

NAND to Inverter conversion

Input a
Input b
Output
Row 1
0
0
1
Row 2
0
1
1
Row 3
1
0
1
Row 4
1
1
0
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