in Digital Logic
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1 vote
1 vote
which is correct?

S1    +ve logic AND operation behaves as -ve logic OR operation.

S2    fxn f(A,B,C)= AB+BC+CA is a self dual fxn.

 

S2 is true but what is the explanation of S1, what does statement 1 want to say?
in Digital Logic
129 views

4 Comments

In positive logic: high voltage is logic 1, low voltage is logic 0

In negative logic: high voltage is logic 0, low voltage is logic 1

Now try to think about this.
0
0
so according to this definition s1 is false?
1
1

Why?

Consider positive logic:

aba.b
000
010
100
111

 

aba+b
000
011
101
111

Complement OR truth table we will get negative logic OR operation

aba+b
111
100
010
000

This truth table is same as positive logic AND operation 
So S1 is true.

2
2
got it..thanks

m last step me mistake kr ra tha..
2
2

1 Answer

1 vote
1 vote

AND Gate Truth Table :

A B A.B
High High High
High Low Low
Low High Low
Low Low Low

 

This table interpreted in +ive logic gives:

       High → 1 and Low → 0

A B A.B
1 1 1
1 0 0
0 1 0
0 0 0

 

 

If the 1st table is interpreted in -ive logic then:

      High → 0 and Low → 1

A B A.B
0 0 0
0 1 1
1 0 1
1 1 1

 

 

In above table A.B is 0 only when A and B both are 0 which is property of OR gate. Hence from above table we can conclude that AND gate in -ive logic system acts as OR gate.