# logic functions?

Discussion in 'Homework Help' started by harvez_007, Nov 8, 2008.

1. ### harvez_007 Thread Starter New Member

May 2, 2008
2
0
Hi.

I am having heaps of trouble understanding how this works:

____________
______
___ __
X = A.B + A + C ?

How do i draw a logic circuit using this function?

What do all the lines mean and do?

Could you please explain it to me, that would be great

Cheers.

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
A' means A with the line above because i cant write it. It means that the value of A is inverted, that if A=1 then A'=0 or if A=0 then A'=1

In the logic function it means that you put a NOT gate after the function that is inverted.
For example, if you want the logic circuit of (AB)' you will put an AND gate and then a NOT gate on the output of the AND gate.
If you have A', then you put a NOT gate on the output of A which is a signal from a device.

In your case, (AB)' means that you need an AND gate (for AB) and a NOT gate on its output (to implement the inversion noted by ') which is equivalent to a NAND gate. Then you will need a 3 input OR gate, on its inputs you will connect the output of the NAND gate, the A input signal and the C input signal. Finally, to implement the inversion denoted by X' you put a NOT gate on the output of the OR gate.