inverted Op Amp question

[oran.outan]

Hi,

Sorry for the simple question but I'm very confuse, WHY ? and have spend most of the day on it... So, if any one can enlighten me !

I've made a very simple inverting unity gain with a TL071 Op Amp, signal pass thru but !
- when I'm using a single supply (+12v) the signal is NOT inverted !
- when using a dual power +/-12v the signal is inverted !

is it not supposed to be always inverted ??? whatever it's single or dual.
What can I do wrong !?
I'm looking to use it with a single supply...

thanks for your help°°°
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[KrIVIUM2323]

Hi,
Have you provided an half supply reference/bias to your non inverting input? If yes do you have a serial resistor of approximately same value as your inverting input input impedance? edit: i read too fast if unity gain i think it could not work, see document linked for other way to approach this.
Could you draw/provide a schem of your protoboard circuit?

Check fig 5 and 6 (and text where they explain what happen)of this: https://www.ti.com/lit/pdf/SLOA030A

 

[oran.outan]

Hi,

Thanks for the link, I can see I have few things wrong and provided wrong the reference.
I will have to make few change
here is my schematic for now...

 

[JohnRoberts]

That's you problem... look for single supply examples...

JR

 

[KrIVIUM2323]

It can't work as you don't have a reference point for the opamp ( ground=-V) you can't reproduce negative occurence.
https://www.ti.com/jp/lit/pdf/sboa059
https://www.analog.com/en/resources/app-notes/an-581.html

 

[radardoug]

The plus input needs to sit at half the supply voltage. Make a divider with two 10K resistors, midpoint to the plus input.

 

[oran.outan]

Have make the changes and now it's inverted...
but some buzzing appear°°°
Will have to dig more...

thanks you all
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[Newmarket]

Supply -12V to OpAmp V-.
Or bias the opamp to +6V as others have suggested. See standard guitar FX pedal schematics for examples of this.