Single supply and split / dual supply

Hello. Is it true that all split or dual supply opamps can be operated in single supply mode, but the inverse is not true?

Thanks!

Reply to
MRW
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All opamps can be operated by any combination of supplies that does not exceed their maximum voltage ratings, but add up to enough voltage to make their input and output stages function.

Rail-to-rail opamps tend to have lower maximum voltage ratings, but also lower minimum voltage ratings. Their claim to fame is having both input and output stages that can deal with signal swings that fall anywhere between the supply rails.

So called single supply opamps generally have lower minimum voltage requirements than dual supply opamps and also input and output stages that function very close to the negative supply rail.

So called dual supply (anything not called rail-to-rail or single supply) generally have higher maximum voltage ratings, but need 1.5 to 4 volts between the input and output voltage swings and the supply rails for their inputs and outputs to function properly. A few JFET input opamps have input stages that function all the way to the positive supply rail.

But any opamp has no way of 'knowing' whether it is being supplied by a single supply, with the inputs somehow biased between those two rails, or by two supplies in series, with the inputs somehow biased between the two supply rails.

Reply to
John Popelish

Very informative! Thanks, John!

Reply to
MRW

The name 'single supply op-amp' is a little misleading. Any op-amp can be operated on a 'single supply' with appropriate biasing of the inputs.

The difference is that 'single supply op-amps' function correctly when their inputs are at ground (negative supply) potential and typically their output can also swing (close) to ground as well. More average op-amps will only function correctly with their inputs several volts away from the supply (see input common mode and differential mode voltage range) and likewise the output will normally not swing close to the supply rails.

Graham

Reply to
Eeyore

I've not seen an op-amp that needed an earth connection to operate, but should such exist it would need a split supply.

Some op-amps can't approach the rails, these may be unsuitable for some single-ended supply applications.

Bye. Jasen

Reply to
Jasen Betts

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