Why do you keep on posting that circuit. I have told you already it will not work because the biasing is none existent on the front end.
Two reasons Mike: first it is somewhat working, apart for that resonance effect I've noticed, and second because it is what I've currently built and I'm trying to "fix".
Now, if I understand you, there's no biasing on the opamp output (I understand that) but I thought biasing was referring to an input voltage. Nonetheless, because the supply voltage is +/-6V with no biasing (is it correct to say ground biasing?) I should get a +/-6V output, with gain given by G=1+(R3/R5).
Is the above statement correct referring my wrong circuit?
When I talk of the pot I was referring to the pot in the correct diagram I posted not your diagram.
Ok, sorry, my bad. I'll apply your suggestions as soon as I understand what's wrong with the current circuit. Please be patient, I'm a tough student
Actually I'm powering the opamp with 12V, splitted into +6V and -6V....
Why? If you do that you will need protection on the arduino's input. Use two diodes, input to cathode and anode to +5V for one. input to anode cathode to ground for the other.
I'm using 12V because I've read the TL082 needs a negative input voltage and I actually got it somewhat working by using that voltage splitter.
In regards to the two diodes, are those there to prevent inverted current to flow into the Arduino?
@rlogiacco - if you are not prepared to take advice then do not ask for it.
Don't misunderstand me Mike, I'm not debating your suggestions and I'm thankful for your advices, I'm trying to understand the reasons behind them because I'm unable to apply them unless I understand them.
As an example, you gave me a diagram for an inverting amplifier with a grounded negative supply, which I already tried and it appeared non working for a TL082. I can try that exact circuit this afternoon, but I doubt it will work because accordingly to the specs the TL082 requires a negative supply voltage.
Among the other suggestions I received there were some regarding a two step gain, which I understand and I did appreciate, but that's not what I need and I believe they apply to complex audio outputs (HiFi and such): all I need is to take a +/- 0.25V sine wave input and boost it to 0/5V, inverting or not.
Right now I'm operating around a TL082 because that's what I currently have, I'll switch to an LM358 as soon as it'll be around.
So, please keep posting your suggestions and I'll do my best to understand them, but I'm unable to apply them blindly, mostly because I need to understand what I'm doing. I hope you don't mind and you'll keep trying to help me.