# Arduino Uno: -5V voltage for op-amp without additional power supply

Hello everybody,
I would have the following question:

I would like a sine wave voltage that is generated by an Arduino Uno via PWM (or DDS) and then brought to a level of -2.5V to 2.5V with a capacitor from the 0V to 5V range, to a level amplify from -5V to 5V.

I have for this purpose an op-amp in non-inverting amplifier circuit provided, more specifically a LM358.

Regardless of which model, need an Op-Amp, to my knowledge, always a supply voltage which is at least as large as the voltage range to which it is to reinforce, so in my case a symmetrical supply of at least -5V and + 5V ,
Actually, you would need a bit more to get exactly the amplitude of the output voltage from -5V to + 5V, but that’s not so important in my case so the gain factor does not have to be exactly 2.

Therefore, I would use for the + 5V supply of the Op-Amps the 5V output pin of the Arduino Uno (which in turn is powered by the intended power supply).
The question now is if I (provided the maximum power delivered by the
5V pins allows) just a parallel tap on a CMOS level converter as the TL7660 can do and take me from this the -5V for the negative supply of the Op-Amp.
As I mean it exactly, the attached sketch can be found.

Has anyone ever happened to have a similar configuration, as in my attached sketch, in operation and could tell me if such a thing (sometimes quite independent of the dimensioning of the circuit) could work or not?

regards
Rabobsel

Looks fine. Be advised, that output of LM358 is going up to +V, about 1.5V below, leaving span -5V ... +3.5V

You have no DC bias to the non-inverting input of the opamp, it can't work without this. Suggest a resistor of 100k or so to ground, the capacitor from the LPF coupling straight to non-inverting pin

The LM358 is a slow opamp, what frequencies are you wanting to use?

The LM358 is not rail-to-rail on the output so +/-5V supply is not enough.

I'd suggest choosing a rail-to-rail opamp.

MarkT:
You have no DC bias to the non-inverting input of the opamp, it can’t work without this. Suggest a resistor of
100k or so to ground, the capacitor from the LPF coupling straight to non-inverting pin

The LM358 is a slow opamp, what frequencies are you wanting to use?

The LM358 is not rail-to-rail on the output so +/-5V supply is not enough.

I’d suggest choosing a rail-to-rail opamp.

Ok thanks, i saw the mistake, i will put R2 to Ground.

Frequency will be 50Hz to 1800Hz

Would the MCP6001 be a valid Choice for Rail-to-Rail Op-Amp ?

Do you think the longitudinal regulator of the 5V output of the Arduino will cope with the increased current consumption (IC + Op-Amp etc.)?

Greetings

Rabobsel: Would the MCP6001 be a valid Choice for Rail-to-Rail Op-Amp ?

No. It is limited to 6V supply voltage.

Ok thx, I will look for another Op-Amp then.