I looked for resources to find solutions to these kinds of problems online, but I couldn't find them. Please, feel free to recommend resources to study from. This is a homework question. I can't find the answers to this. I read the chapters of the book.

We need to connect outputs of circuit A to inputs of circuit B.

Circuit A has the following parameters: Powered by 5V source. V output high minimum is 2.7V. V output low maximum is 0.5V. I output high is 400uA. I output low is 16mA.

Circuit B has the following parameters: Powered by 3.3V source. V input high minimum is 2.3V. V input low maximum is 1V. I input is 1uA.

For the proposed way of connecting the circuits, A and B are compatible for low logical value, both voltage and current vise. The question is, are they compatible for high logical value? If they are not, how to make them compatible?

Here is a photo to simplify things: Voltage levels visualized

How would it affect compatibility for high logical level if we changed one parameter of circuit A - V output high minimum is 3.5V?

B circuit - New minimum high output voltage visualized

  • 1
    \$\begingroup\$ Possible duplicate of 5v output to 3.3v? \$\endgroup\$ Sep 25, 2018 at 19:12
  • \$\begingroup\$ Shocky2 - Some of the available options depend on characteristics of "Circuit B" that you haven't given us. Please can you give us some context e.g. are these two "circuits" (devices?) actually known to you (in which case, please give us part numbers or whatever details you have) or is this some kind of homework and the tutor is deliberately making it a hypothetical / generic question? \$\endgroup\$
    – SamGibson
    Sep 25, 2018 at 19:14
  • \$\begingroup\$ @SamGibson Thank you for your response. This is some kind of homework. Everything I had is there. \$\endgroup\$
    – Shocky2
    Sep 25, 2018 at 19:57
  • \$\begingroup\$ @JakubRakus Sadly, this is not a duplicate. This is a homework question. I am sorry, I can't answer it. Please, if you know the answer, I would appreciate the help. \$\endgroup\$
    – Shocky2
    Sep 25, 2018 at 20:00

1 Answer 1


If this is an actual project you can see the maximum logic high input voltage of the component in their datasheet.

But since this is a theoretical question from a homework then i will just point you to the right direction. Look for voltage clipping and you should have your answer.

  • \$\begingroup\$ The simplest way will be through voltage clipping if it is just a simple ON/OFF logic purpose. If that is for data communication purpose then you'll need to go use transistors to shift the logic or use dedicated logic level shifter ic. \$\endgroup\$
    – Zy Gan
    Sep 26, 2018 at 8:10

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