Op amp not working out as planned

[StillTrying]

With a 100MHz op amp on a bread board with long leads I'm surprised you're getting anything other than oscillation!

100nF directly across it's supply pins 4,7, I'd be tempted to solder it on top of the carrier.
Replace some of the long breadboard leads with short 1 core wires.
Apply the +ve input adjust voltage through a ~4k7 resistor, and with a 100n to 1u cap between the +ve input and 0V. With a gain of -2 the voltage on the +ve input will only be adjustable between about 3V and 8V before the output clips at it's limits.

[netdudeuk]

I've had some time away from this project but I'm back on it 

I've set up a split rail supply for the op amp along with the 5v for the DDS and microcontroller.

There's an analogue ground from the DDS along with the digital one.  I guess the former is the right one to use.

The question is though, as the DDS and microcontroller have their own common 0v / ground line and the op amp doesn't, how do I connect this side of things to the op amp ?  And similarly, the op amp has an output but where's the equivalent 'ground reference' ?

I'd like to use the DS1054Z to show me the input and output traces to confirm operation.  While the scope ground on the input channel will connect ok to the DDS / microcontroller 'digital ground', I don't want to blow something up but putting the scope ground on the output channel to the wrong potential and cause a short.

Please forgive any bad terminology.

Thanks

[rstofer]

The question is though, as the DDS and microcontroller have their own common 0v / ground line and the op amp doesn't, how do I connect this side of things to the op amp ?  And similarly, the op amp has an output but where's the equivalent 'ground reference' ?

I haven't kept up the various op amps and power supplies so this may be completely wrong...

The center point of your +-15V power supplies is ground.  If you ground both op amp inputs to this point, you should measure an output voltage of 0V relative to this ground.  In any event, you should have one supply that measures +15V to ground and the other measures -15V to ground.  This being the case, the output of the op amp can swing above and below ground.  How close the output can get to the rails is a datasheet issue.

Your other grounds should connect to this ground reference including your 5V supply, your single ended DDS gadget and your scope ground.

With dual supplies it's pretty easy to figure out where ground is.  In the case of single supplies, we have to create a virtual ground at 1/2 the rail voltage and somehow connect all the other grounds to that point.