need a -5V supply...

[dtvonly]

Hi. can I use an inverting op amp with a +5V input to get a -5V output, for use to run other op amps that needs +/-5V? This will be a low current application. Please see attachment.

Thank you.

 

[Boncuk]

What format is the file when unzipped?

Can't read it.

Besides that I suggest to use a MAX1721. +5V in -> -5V/25mA out, clean with only two tantalum caps.

 

[KMoffett]

It's a Microsoft WORD 2007 document...".docx"

dtvonly,

Save the document in the "95-2003" format. Many people don't have the newer WORD versions.

ken

 

[MrDEB]

why not use a 7805 thats is a negative output?
not sure of part number

 

[MikeMl]

The answer to the OP's question is NO. An OPAMP can pull its output near -5V IF AND ONLY IF its V- supply pin is tied to a NEGATIVE power supply. You are trying to invent PERPETUAL MOTION

 

[crutschow]

Your simulation worked only because your "IDEAL" op amp has build-in internal positive and negative supply voltages. If you use an op amp for U1 that requires external supplies, like U2, you will see that your simulation will not work (as would be true in real life).

 

[WindWalker]

why not use a 7805 thats is a negative output?
not sure of part number

It's LM7905 (negative), not LM7805 (positive).

 

[audioguru]

Without seeing the schematic we are just guessing. I don't know why the schematic is hidden in a zipped Word document.
I think he wants to convert +5V to make -5V. A 7905 negative regulator does not convert a positive voltage into a negative voltage.
An ICL7660 IC charge-pump IC can do it but its output current is low.

 

[creakndale]

Check out the CUI Inc., V-Infinity Series of DC-DC converters. +5V input with +/-5V outputs.

creakndale

 

[Boncuk]

or this.

Here's a datasheet.

Input and output are isolated. Connecting +Vout to ground makes -Vout negative.

 

[Hero999]

If you don't have MS Word then you can download a free viewer but unfortunately it's Windows only, although OpenOffice.org will open some MS Word files.

I would ban the uploading of Word documents myself.

Anyway, here's the schematic in PNG format, goodness knows why the OP didn't just post it in PNG in the first place.

Would it ba acceptable to bias at half the supply voltage so you can use a single power supply?

EDIT:

Just looked at the schematic again, it doesn't look right to me. Why is the 0V of the second op-amp connected to the output of the first?

If it's to bias the AC voltage at a certain DC level, it isn't the right way of doing it, a potential divider should be used.

 

[audioguru]

Just looked at the schematic again, it doesn't look right to me. Why is the 0V of the second opamp connected to the output of the first?

Post #6 says that the "ideal" opamp for the first opamp has a positive and negative supply so its output is -5V. Then the second opamp also has a positive and negative supply.

 

[Hero999]

Lol, I can see what the original poster's done, they're using an ideal inverting amplifier with a built-in negative supply to get a negative rail for a non-ideal op-amp.

This will never work in real life because a real non-ideal op-amp will require a negative supply and so will an LM7905.

It's a Microsoft WORD 2007 document...".docx"

dtvonly,

Save the document in the "95-2003" format. Many people don't have the newer WORD versions.

ken

Download the compatibility pack: this works with all MS versions since 2000 as well as the free viewer.

**broken link removed**

Or alternatively the latest version of OpenOffice.org

OpenOffice.org - The Free and Open Productivity Suite