# Converting/scaling a voltage range ([0v - 5v] to [-5v - +5v])

Can anyone explain how one would convert one voltage range to another? I'm going to need to convert a range of 0 to +5 volts into a range of -5 to +5 volts. How would this be accomplished? Thanks!

For working with power conversions rather than signal -

You can use various integrated circuits for this job, they're commonly referred to as Dc to DC converters, there's also a range of ways to do the conversion such as Charge pumps.

Here's a bunch of different DC to DC converters they have various different current ratings, some step the voltage up, some step down and others convert between positive and negative values.

This is a nice charge pump IC that can double or invert a voltage with the minimum of external components. You could even use a 555 timer to convert a voltage to a negative

Hope this helps.

• I am giving a +1, i am not sure if he wants something for power, or if it is a signal, you did power, i did signal. – Kortuk Jun 16 '10 at 16:36
• I've also had success with CMOS voltage converters (national.com/mpf/LM/LMC7660.html#Overview) they're easy to use but limited in their usefulness – Jim Jun 16 '10 at 16:37
• Thanks guys, this gives me a lot to go with - I'll check it all out. – Greg Jun 16 '10 at 16:53
• So are you trying to make dual power supplies Greg? – Kortuk Jun 16 '10 at 19:19
• No, doing some work with a DAC-based idea, where I'll need to scale the voltage output. – Greg Jun 16 '10 at 23:06

There are many ways to do this, the easiest I think would be a summing op-amp configuration.

I want to try using this ascii system, lets see how it does. This is a circuit that does what you want.

          -5V
|
.-.
| |
| |2K           2K_
'-'       .----|___|----.
|        |             |
|        |             |
'--------o             |
|      +Pwr   |
___          |    |\|      |
input-|___|---------o----|-\      |
1K                |  >-----o----Output
.----|+/
|    |/|
GND     -Pwr

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)


So, it takes the input, doubles it and subtracts 5 V.

This will make 2.5V become 0V, 0V becomes -5V, and 5V stays 5V.

It does it linearly over the range, this can be valuable if it is a signal that needs to be spread over a new range.

Hope this helped.

• This solution is for a signal, if you want to power a system with it, i may have missunderstood you. – Kortuk Jun 16 '10 at 16:31
• Cheers for pointing that out, I missed that one - doh! – Jim Jun 16 '10 at 16:38
• Nice diagram - they look kinda retro! – Jim Jun 16 '10 at 16:40
• They are awesome, want links? chiphacker.com/questions/1024/… – Kortuk Jun 16 '10 at 16:58
• That is how I learned about it, and I think I love it. – Kortuk Jun 16 '10 at 16:58
          +5V
|
.-.
| |
| |2K           2K_
'-'       .----|___|----.
|        |             |
|        |             |
'--------o             |
|      +Pwr   |
|    |\|      |
.----|-\      |
|  >-----o----Output
input--------------------|+/
|/|
-Pwr

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)


This will make 2.5V become 0V, 0V becomes -5V, and 5V stays 5V.

The circuit posted by Kortuk will invert the input resulting in a mapping from [0v -> 5v] to [+5v -> -5v] instead of [0v -> 5v] to [-5v -> +5v].

Here is a simulation.