negative voltage

[keckclip]

Hi, I'm sort of a newbie at electronics and am trying to figure out how to produce a negative voltage when having only a positive source. I've done some research and come across various chips such as MAX1044 charge pump converter and some inverting regulators. There have also been suggestions of making a 'virtual ground' but I don't really understand that. All in all I'd like to know how to feed pos and neg voltage to op-amps and whatnot on test circuits using, for instance, only a 15V DC adapter. Any help is appreciated.

Thanks

 

[QuietMan]

You need to state specs when you post something like this. There are lots of ways to do it, but we can't cull them out unless we know what you're shooting for.

Have you read this?

Creating a Virtual Power Supply Ground

 

[BeeBop]

Hi, I'm sort of a newbie at electronics and am trying to figure out how to produce a negative voltage when having only a positive source. I've done some research and come across various chips such as MAX1044 charge pump converter and some inverting regulators. There have also been suggestions of making a 'virtual ground' but I don't really understand that. All in all I'd like to know how to feed pos and neg voltage to op-amps and whatnot on test circuits using, for instance, only a 15V DC adapter. Any help is appreciated.

Thanks

Hi,
similar questions have been asked so often that there is a sticky for this:
Dual or single supplies for opamps.

hope that explains enough for you.

What people mean when they use the term 'virtual ground' in this context is using an equally matched series of two resistors between V+ and V-. This is not really what virtual ground means, however, this voltage divider will divide the source voltage in half, so if you use the tap between the resistors as your ground, then V+ is at one half the source voltage, and V- is negative one half the source voltage.

You may want to google voltage divider.
regards

 

[keckclip]

You need to state specs when you post something like this. There are lots of ways to do it, but we can't cull them out unless we know what you're shooting for.

Have you read this?

Creating a Virtual Power Supply Ground

Hi, as an example I would basically like to take +15V and generate -15V on my protoboard. I've seen a similar article with respect to virtual grounds but am unsure how to implement this without the use of batteries, as in the examples.

 

[keckclip]

Hi,
similar questions have been asked so often that there is a sticky for this:
Dual or single supplies for opamps.

hope that explains enough for you.

What people mean when they use the term 'virtual ground' in this context is using an equally matched series of two resistors between V+ and V-. This is not really what virtual ground means, however, this voltage divider will divide the source voltage in half, so if you use the tap between the resistors as your ground, then V+ is at one half the source voltage, and V- is negative one half the source voltage.

You may want to google voltage divider.
regards

Yes I did see the stickies after I had already posted reminding me again to practice the art of patience I'm going through the Texas Instruments article now as it seems very helpful in explaining the virtual ground technique. Thank you all for your replies.

 

[Salgat]

If you set your ground at a 7.5V, you will end up with 0V appearing as -7.5V and 15V appearing as +7.5V to your circuit. Remember, all that matters is voltage difference and voltage polarity, ground is whatever you want it to be.

 

[keckclip]

If you set your ground at a 7.5V, you will end up with 0V appearing as -7.5V and 15V appearing as +7.5V to your circuit. Remember, all that matters is voltage difference and voltage polarity, ground is whatever you want it to be.

Ahh, 7.5V will be my virtual ground, ok I think I understand. So it is possible to substitute single supply op-amp for (almost) any dual supply configurations by implementing a virtual ground? Thanks a lot!

 

[audioguru]

Any opamp will work with a single supply if its inputs are biased at half the supply voltage. Just the (+) input needs to be biased and the (-) input is biaed from its output.
A single supply opamp is unique because it will also work with its inputs biased at 0V.