1. Oct 14, 2008

### marlboro73

hey guys.. can u pls help me solve this problem. i have some answers but im just not really sure if they're right. pls help me. my exam starts in a few hours

here's the problem:

The truth table of a full adder circuit is given below, where A and B are two inputs and Cin is the carry from the previous bits.

http://img513.imageshack.us/img513/8765/truthtableeu5.th.jpg [Broken]http://g.imageshack.us/thpix.php [Broken]

i) Get the output expression for sum and carry from the truth table.

ii) use Boolean Algebra to simplify Sum only to an XOR gate

iii) Derive the expression for the carry and simplify it using Boolean algebra.
iv) Draw the full circuit showing the inputs, sum and the carry.

e) Using Boolean algebra and De- Morgan’s or otherwise prove the property
f) State and prove De- Morgan’s law for three input variables
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 3, 2017
2. Oct 15, 2008

### Ouabache

Welcome to PF forums!! You will find there are many fascinating useful discussions here on all kinds of topics (most of them science related).

That's an interesting question. It is good, that you have worked out some soln's to your problem. Before we can help you, you need to post your thoughts, a sequence of how you attempted a solution. Then ask questions regarding your attempt.. You probably want to reread this https://www.physicsforums.com/showthread.php?t=94388"to help guide you on posts. It is also listed at the top of this homework area under "why hasn't anybody answered my question".

Last edited by a moderator: Apr 23, 2017