+9v and -9v

[swinginguitar]

Been looking at some circuits that use 2 batteries to produce a + and - 9v reference to either side of an opamp (for buffers/transformer couplers)

1) how could this be accomplished with either 2 9v power supplies or 1 18v supply?

2) how is this diffrent than voltage division for a Vref with the op amp tied to V+ and ground?

[CynicalMan]

Been looking at some circuits that use 2 batteries to produce a + and - 9v reference to either side of an opamp (for buffers/transformer couplers)

1) how could this be accomplished with either 2 9v power supplies or 1 18v supply?

Use a virtual ground, or, with a 9V supply, IC7660S or MAX1044 voltage doubler and a virtual ground (Vref).

2) how is this diffrent than voltage division for a Vref with the op amp tied to V+ and ground?

It's simpler and easier to design. There are a few cases, such as driving an LED, where having a virtual ground is an issue, but they don't come up often.

[petemoore]

  way OT...
  Sittin' here giving "Working Man'' a spin when I glance to see what's up in the forum today and see: "Alex L.'' .... ''Canada'' in this thread.
  Just curious if these three things are amazing coincidence or they/you are otherwise related.

[CynicalMan]

Lol
No. I'm not even a Rush fan. Had to google that one.   

[darron]

to expand on CynicalMan:

http://www.geofex.com/circuits/+9_to_-9.htm