What is the output for the following logic circuit?

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    Circuit Logic Output
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Discussion Overview

The discussion revolves around the output of a specific logic circuit, with participants analyzing the correctness of a provided solution and exploring the implications of different logic gate configurations. The scope includes technical reasoning and verification of circuit behavior.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a detailed derivation of the circuit output, concluding with the expression A'+B+C' and expressing confusion over discrepancies with the expected output.
  • Another participant agrees with the first, suggesting that the presence of C in the final output indicates that +C' should be included in the correct answer.
  • A third participant questions the alignment between the circuit diagram and the provided explanation, noting inconsistencies in the gate types described.
  • A participant shares a Verilog module that simulates the circuit, confirming the output A'+B+C' through a truth table.
  • One participant mentions an erratum in a study guide related to the problem, expressing uncertainty about the original solution's accuracy and indicating a belief that it is a mistake.

Areas of Agreement / Disagreement

Participants express disagreement regarding the correctness of the provided solution, with multiple competing views on the output of the logic circuit and the interpretation of the gates involved. The discussion remains unresolved as participants continue to analyze the problem.

Contextual Notes

There are limitations related to the assumptions made about the circuit configuration and the definitions of the gates, which may affect the interpretations of the outputs. The discrepancies between the circuit diagram and the explanation are also noted but not resolved.

Who May Find This Useful

This discussion may be useful for individuals studying digital logic design, preparing for engineering exams, or seeking clarification on logic circuit outputs and configurations.

icesalmon
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Homework Statement
What is the output for the following logic circuit?
Relevant Equations
DeMorgan's Law
Logical Operations involving Logic Gates
I obtained the following result:
([(A xor B) xor 0]* AC)'
([(A'B + AB') xor (0)]*AC)'
[([A'B + AB']*(0)' + 0)*AC)]'
[(A'B + AB')*(1)*(AC)]'
[A'ABC + AB'AC]'
[AB'C]'
A'+B+C'
the solution to this problem is getting a different answer, I don't know why this solution isn't inverting the output AB'C
 

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I agree with your answer. I think the simplest way to see that the given answer is wrong is to consider how C appears in it. The only appearance of C is as an input to the final NAND. It seems that +C' must be in the correct answer.
 
FactChecker said:
I think the simplest way to see that the given answer is wrong

I was looking back and forth and at the given answer and wondering if the circuit and the explanation actually even go together. The explanation says the second gate is a NOR and the last gate is an AND but that's not what's drawn.

Code:
module problem2;
wire A,B,C,out;
reg [2:0] x;
assign out = !( A & C & (0^(A^B)) );
assign {A,B,C}=x[2:0];
initial begin
  $display("A B C | O");
  x=0;
  do begin
    #1 $display("%b %b %b | %b",A,B,C,out);
    x=x+1;
  end while(x!=0);
end
endmodule

Which yields A'+B+C'

Code:
A B C | O
0 0 0 | 1
0 0 1 | 1
0 1 0 | 1
0 1 1 | 1
1 0 0 | 1
1 0 1 | 0
1 1 0 | 1
1 1 1 | 1
 
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the errata for a study guide I'm using to prepare for the Fundamentals of Engineering Exam didn't include this correction and was issued in 2017 so I decided to ask here. The solution I included corresponded to the problem I posted in the study guide, I'm not sure what happened with the solution to this problem when it was written. But I'm convinced this is a mistake. Thanks for the help in verifying that it was a mistake, i'll just flag the problem and move on.
 
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