# problem with buffer

Discussion in 'Homework Help' started by mateusz, Feb 10, 2013.

1. ### mateusz Thread Starter New Member

Feb 10, 2013
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0
Hello.
I have a problem with one task.

Using only three-condition buffer and one resistor design a circuit which functionality is the same as buffer with open-collector. Can any one help me with this ?

Last edited: Feb 10, 2013
2. ### WBahn Moderator

Mar 31, 2012
23,214
6,999
What attempts have you made to solve the problem so far?

3. ### mateusz Thread Starter New Member

Feb 10, 2013
3
0
Last edited: Feb 10, 2013
4. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
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Try looking for a THREE-conditon buffer or Tri-State Buffer.

edit and then I make a typo on condition...

Last edited: Feb 10, 2013

Feb 10, 2013
3
0
Thank you

6. ### WBahn Moderator

Mar 31, 2012
23,214
6,999
But you don't need the circuits. You need to know how they behave.

You have a black box that I tell you is an open collector buffer. What do you expect to see? How many inputs? How many outputs? How do you expect the outputs to respond the inputs?

Now you have a black box that I tell you is an "three-condition" buffer, also known as a "three-state" or "tri-state" buffer. Same questions? What do you you expect to see and how do you expect it to behave?

The goal is to take one of the black boxes that is a three-state buffer and a resistor and put that inside the other box and hook it up so that you can't tell that it has that inside instead of an actual open-collector buffer.

Now, some issues that might cause you problems: Are you only trying to replicate the open collector buffer, or the typical circuit in which it has a pullup resistor on the output? Is the three-state buffer you are working with have an active HI or an active LO output enable input?