Hooking up a TO82 Opamp

[Andrei]

Hi,

I am trying to hook up a TL082 opamp as a simple non inverting amplifier for the first time. The datasheet for the part is here: http://pdf1.alldatasheet.com/datasheet-pdf/view/173078/UTC/TL082.html

What I am essentially trying to breadboard is http://en.wikipedia.org/wiki/File:Operational_amplifier_noninverting.svg

For the two resistors, I chose them both to be 10K for a 2x closed loop gain. The Vcc- and  Vcc+ are -5V/5V respectively. The input signal is a sinusoidal waveform of 1Vpp at 1kHz. I expect a 2Vpp output, with some lag.

However, when I flip the switch on on the power supply, the output of the opamp dips to -500mv and stays there with no change. If I dial up or down Vcc+ and Vcc- the output voltage decreases/increases respectively

I checked ground to Vcc+ and it checks out at 5V and ground to Vcc- and it checks out to -5V. Vcc+ to Vcc- gives me about 600mV which seems odd?

Any ideas would be appreciated, I am certain I am doing something incredibly stupid. I verified the input and the output on the scope.

Thanks.

[mushroom]

It could be oscillating...

Here is an image of the output of an op amp (CA3130, single rail 0-5V supply, gain 1 buffer) without compensation capacitor :

[Andrei]

Hi mushroom,


I pulled it up on the scope as well, the output is not oscilating, it is set at a very stable constant -400mV.

[Andy Watson]

....  Vcc+ to Vcc- gives me about 600mV which seems odd?

More than odd! I go as far as to say Wrong  
Either you haven't made a common ground between your power supplies, or you have a short circuit through a diode or other silicon junction.

Edit: Pictures, per chance ?

[Andrei]

Hey Andy,

As it turns out it was a bad lead to Vcc+. Measuring the resistance across that wire lead, it's 0.3M Ohms :S, changing the lead results in expected behaviour. Quite the stupid problem ...

Thanks for all the help!