# Help with this voltage conversion?

Discussion in 'General Electronics Chat' started by jean28, Jul 26, 2013.

1. ### jean28 Thread Starter Member

Sep 5, 2012
76
0
Hello, guys!

I have a little issue. I'm using a micro and from a pin i get either 0V or 5V. I need to pass the voltage from that pin to something else that only works if it gets -2.5V or 2.5V. How can I convert the 0V to -2.5V and the 5V to 2.5V? I know that the 5 -> 2.5 can be done with a voltage divider, but how do I convert the 0 to -2.5 as well?

Thanks!

2. ### odinhg Active Member

Jul 22, 2009
65
15
Do you have a negative voltage supply available in your circuit?
How much current do you need to source?
How fast do you need to switch?
What micro do you use?

Answers to these questions would help others help you

Edit:
I'm still a beginner myself, but I did try to make a circuit that should do what you want. I'm not sure if it is a good solution, but it works in simulator. (Schematic attached)

I did remove the resistor values, but they should be easy for you to figure out on your own. Take a look at the following articles if you're stuck:
http://www.allaboutcircuits.com/vol_1/chpt_6/1.html
http://www.allaboutcircuits.com/vol_3/chpt_8/9.html

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Last edited: Jul 26, 2013
3. ### MrChips Moderator

Oct 2, 2009
17,075
5,281
Add -2.5V to your signal.

4. ### WBahn Moderator

Mar 31, 2012
23,089
6,941
Depending on exactly what you have and what you are doing, you may be able to just refer the second part to half the micro's supply voltage and be done.

5. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
674
Excellent point.
Jean12, tell us the big picture of what you are trying to do.