Simple Opamp Problems LT1006

[trevorth]

Im trying to use an opamp to adjust a regulator. Ive simulated the whole circuit but cant even get the op-amps to work! Im not sure if I have faulty devices...

The opamp is LT1006:
https://www.linear.com/product/LT1006

I have reduced it to just the opamp, very simple circuit. I have tried a second chip incase the first was damaged. The second IC behaves in exactly the same way regardless of load...etc.

Below in pictures:
Opamp on its own in simulator.
Scope output 1 (orange input, purple output) 12V power off.
Scope output 2 (orange input, purple output) 12V power on.
Circuit on board.

This is making me feel very stupid but must be something simple... Is there some part of the specification that Im misunderstanding? I expect the second scope trace to give a large swing as Rf=3.3k and Rg=1.5k ... (3.3/1.5)+1 = 3.2 * 2.5VIN = 5.7V VOUT. V+ is 12V and Ive made sure the current limiter isnt set low, verified all connections...etc. What makes an output like Im seeing? Dodgy IC?

Thanks.

 

[LvW]

Trevorth - Why don`t you use the classical double supply operation?
Single supply requires some special bias provisions. Check your dc quiescent point at the opamp output. What voltage do you expect?

 

[barry]

Trevorth - Why don`t you use the classical double supply operation?
Single supply requires some special bias provisions. Check your dc quiescent point at the opamp output. What voltage do you expect?

This opamp will work perfectly fine with a single supply. Common mode range goes to ground, so as long as the input is positive, there's no issue.

My guess is this is wired incorrectly.

 

[FvM]

To check for possible wiring errors, I would measure the voltage of all connected OP pins against circuit ground with the oscilloscope.