How can I construct 2:4 Decoder circuit with the help of IC74139 (74xx139)

[cikalekli]

This is the Truth Table for IC74139 (74xx139) that 2:4 Decoder:



I just know to construct 1:4 decoder only. And when I build my circuit, it cannot meet the accuracy of that truth table... Can you help me to construct that circuit please?

(Note: I've built it wrongly and to correct my false circuit, you can check my wrong diagram below)

( I did it with "circuitverse" simulation website)

 

[Harald Kapp]

I just know to construct 1:4 decoder only.

Interesting. How can you decode 4 outputs from 1 input? This is impossible with binary logic.

when I build my circuit, it cannot meet the accuracy of that truth table

Show us your circuit, The diagram you posted is of no use.

it cannot meet the accuracy of that truth table

This is not a useful description. Show us where your circuit performs differently.

Can you help me to construct that circuit please?

Construct how? The 74xx139 contains all the circuitry necessary.
The datasheet even shows the internal equivalent logic diagram aka circuit of this chip.

 

[cikalekli]

Interesting. How can you decode 4 outputs from 1 input? This is impossible with binary logic.

Show us your circuit, The diagram you posted is of no use.

This is not a useful description. Show us where your circuit performs differently.

Construct how? The 74xx139 contains all the circuitry necessary.
The datasheet even shows the internal equivalent logic diagram aka circuit of this chip.

That is right, I agree with you. I just thought same things like you. Unfortunately my academician who gave this making diagram thing and according to him, it is possible. Let me give you the exact details which my teacher gave me below:




I just really confused because I could not make any proper diagram circuit just for that thing... I'm really sorry for asking that...

I also found a webpage about this problem in Multisim help page.

 

[cikalekli]

Interesting. How can you decode 4 outputs from 1 input? This is impossible with binary logic.

Show us your circuit, The diagram you posted is of no use.

This is not a useful description. Show us where your circuit performs differently.

Construct how? The 74xx139 contains all the circuitry necessary.
The datasheet even shows the internal equivalent logic diagram aka circuit of this chip.

Also the experiment consist to make 4x1 Multiplexer at the first part and I did it correctly. (you can check my circuit diagram drawing below

 

[Harald Kapp]

I'm afraid I don't really understand the task description.
The 74139 contains two 2-to-4 decoders. All you have to do is map the names of the input signals and output signals from the chip to the ones in the truth table.

Or do you have to construct the 2-to-4 decoder in the circuitverse simulator? If that is the case, your diagram in post #1 is a good start.
You'll have to use additional gates, though. What kind of gate do you have to insert between the outputs of the de-multiplexer and the circuit outputs to generate 0111 instead of 1000 as is currently the case? That should be easy.
Next you'll have to add the enable input which is completely missing from your circuit. You can modify the gates from the previous step to include a second input which is controlled by the enable input to complete the truth table. Note that for enable = 1 all outputs shall be 1, for enable=0 the outputs shall follow the truth table. Which gate would generate a logic 1 output if enable is 1, regardless of the state of the de-multiplexer?

 

[cikalekli]

I'm afraid I don't really understand the task description.
The 74139 contains two 2-to-4 decoders. All you have to do is map the names of the input signals and output signals from the chip to the ones in the truth table.

Or do you have to construct the 2-to-4 decoder in the circuitverse simulator? If that is the case, your diagram in post #1 is a good start.
You'll have to use additional gates, though. What kind of gate do you have to insert between the outputs of the de-multiplexer and the circuit outputs to generate 0111 instead of 1000 as is currently the case? That should be easy.
Next you'll have to add the enable input which is completely missing from your circuit. You can modify the gates from the previous step to include a second input which is controlled by the enable input to complete the truth table. Note that for enable = 1 all outputs shall be 1, for enable=0 the outputs shall follow the truth table. Which gate would generate a logic 1 output if enable is 1, regardless of the state of the de-multiplexer?

You are absolutely right sir, teacher wanted from us construct the 2-to-4 decodervia the circuitverse simulator. Yeah the result was shown always reversely like 0111 instead of 1000 as my current case in post #1. Let me share with you the whole word file for this project to clarify your questions. Im really really sorry for bothering with this harsh and not understable thing... Because this is my first year of as university student and my teacher just put the level bar so high just like that.
Here is the experiment word file, you can find your questions inside it: https://easyupload.io/81vjo2

 

[Harald Kapp]

Follow the path along my questions in post #2. This will lead to the solution.
Please note: It is our policy not to provide complete solutions. We will help you along so you can learn on the way.

 

[cikalekli]

Follow the path along my questions in post #2. This will lead to the solution.
Please note: It is our policy not to provide complete solutions. We will help you along so you can learn on the way.

Ah I followed your explanation and I probably made it right. I know that you cannot give the exact solution, im aware of it sir. Look that simulation which i did please: https://circuitverse.org/users/61737/projects/123-d5469a85-b569-48d9-8265-ee59ed09cc4f

can you try to press buttons to test it whether right of wrong...

 

[Harald Kapp]

The circuit still lacks the enable function.

 

[cikalekli]

The circuit still lacks the enable function.

Yeah your explanations were right. The problem is making this only with circuitverse simulation platform. If the teacher would want just to draw then yeah that would be considerably easier than this.

In the website of circuitverse, there is only one multiplexer and one decoder design enabled to be used.

I really confused and plus that is not a homework, just I have a midtern in first week of january and i wanna be well prepared about the questions which my book was given

 

[Harald Kapp]

In the website of circuitverse, there is only one multiplexer and one decoder design enabled to be used.

That's enough for this task. To complete the enable function use logic gates which can be used in addition to the multiplexer.

 

[cikalekli]

That's enough for this task. To complete the enable function use logic gates which can be used in addition to the multiplexer.

Thank you