Converting dual or balanced supply circuit to single supply?
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Posted by MRW on June 19, 2007, 10:46 am
Please log in for more thread options 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! | |||||||||||||
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Posted by John Popelish on June 19, 2007, 11:04 am
Please log in for more thread options MRW wrote: 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. > I probably need to take this into account:
> http://pdfserv.maxim-ic.com/en/an/AN1877.pdf > > Thanks! > | |||||||||||||
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Posted by MRW on June 19, 2007, 11:24 am
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> 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! | |||||||||||||
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Posted by Phil Allison on June 20, 2007, 12:14 am
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"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 | |||||||||||||
> 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?