Is it possible to use a single supply op amp and have it powered by two voltages (ie vdd, -vdd)?

 

hi 486,
Do you have a particular OPA in mind.?
They do vary in their specifications regarding supplies.
E

 

In general it's not problem to power a single-supply op amp from dual supplies, as long as all the op amps voltage (supply and common-mode) limits are not exceeded.

 

Is it possible to use a single supply op amp and have it powered by two voltages (ie vdd, -vdd)?

Yes.

A "single supply" op amp is merely an op amp with characteristics that make it easy to use with only a single (usually +) supply voltage. The most common of these characteristics is an input voltage range that extends all the way down to the voltage on the (-) supply pin. Also common is an output that can swing the full range between the (-) to (+) supplies.

But in truth, any op amp can be used with only a single supply or with (+) and (-) supplies-- it's just a question of how conveniently.

 

Generally, they don;t output to the power rails. Some can get very close.

An LM324 is an exception. Very far from the + rail.

Inputs can't usually exceed the rails. Generally, it's less than a Shotkey diode drop without protection. Then some Over the Top technology OP-amps can.

As was stated, check the common mode range of the inputs.

You also need to look at the OP-amp and it's associated circuity if the OP amp can have an inout and not have power. That makes the +rail 0V.

 

All opamps use a single supply since there is no ground connection on the opamp (I am sure someone will come up with a counterexample, but they are not common.)

OBW0549 stated what make an opamp good for use with a single supply.

You can use an ancient 741 with a single supply, but the voltages on the inputs and outputs will have to be kept around 2V away from ground or the positive supply.

An even more useful opamp is called rail-to-rail, which allows inputs and outputs go go all the way to both ground and the supply voltage.

Bob

 

Ditto what @BobTPH said.

"Dual supply" = this op-amp cannot output to either power rail
"Single supply" = this op-amp can output (near) to one of the power rails
"Rail to rail" = this op-amp can output (near) to both power rails

It's just lingo that is suggestive of how the particular op-amp might be used.

 

A good reading about that, especifically chapters 4 and 18
http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf

 

Thanks! I had a suspicion that was case. there was one op amp that I was looking at on digikey (closed the window...sorry!) that said single supply operation, but did not go on to say the split volt range. End up not caring though because I really need it to be rail to rail in and out and that did not fit the bill.

 

...I really need it to be rail to rail in and out and that did not fit the bill.

Two rail-to-rail input/output op amps I've used often are the LMC6482 and the LT1490A.

 

The LM324 is a quad op-amp that is cheap and easy to work with and available from several manufacturers. It can be used with a split supply or as a single supply device. The lower frequency response makes it a bit less likely to oscillate , which is handy for experimenting. So it depends on what you want to achieve.