Converting dual or balanced supply circuit to single supply?

[MRW]

Hi, I have a schematic of an opamp circuit that is biased by a
positive and negative voltage source. I was thinking I can convert it
to single supply by doing the following:

- replace ground reference of dual supply circuit with Vcc/2 .
- replace negative reference of dual supply circuit with 0V.

Is this a correct assumption? What other things do I need to take into
account?

I probably need to take this into account:
http://pdfserv.maxim-ic.com/en/an/AN1877.pdf

Thanks!

 

[John Popelish]

Hi, I have a schematic of an opamp circuit that is biased by a
positive and negative voltage source. I was thinking I can convert it
to single supply by doing the following:

- replace ground reference of dual supply circuit with Vcc/2 .
- replace negative reference of dual supply circuit with 0V.

Is this a correct assumption? What other things do I need to take into
account?

That should do it, if you include the fact that the output
swing will be reduced to the lower supply voltage and the
inputs have to deal with being re referenced to your Vcc/2
voltage. If this causes them to pass current to that
reference, they may "talk" to each other through this node.

 

[MRW]

That should do it, if you include the fact that the output
swing will be reduced to the lower supply voltage and the
inputs have to deal with being re referenced to your Vcc/2
voltage. If this causes them to pass current to that
reference, they may "talk" to each other through this node.

Thanks, John!

 

[Phil Allison]

"MRW"

Hi, I have a schematic of an opamp circuit that is biased by a
positive and negative voltage source. I was thinking I can convert it
to single supply by doing the following:

- replace ground reference of dual supply circuit with Vcc/2 .
- replace negative reference of dual supply circuit with 0V.

Is this a correct assumption? What other things do I need to take into
account?

** Generally you cannot do that.

The ground " reference" for input and output signals becomes the same
conductor as the negative ( of the now single supply) uses.

What you really do is create a "half rail " DC reference that is used
solely to bias the op-amp ins and outs to that voltage.

Then, all outside world inputs and outputs are coupled via capacitors that
block the half rail voltage.



....... Phil