Electronic – arduino – Single supply op amp to convert 0-5VDC to +/-2VDC (microcontroller to line level)

arduinoaudiobiasdcoperational-amplifier

I am generating a 0-5 volt sine wave using an arduino with a DAC.
I would like to level shift this signal (DC bias?) by -2.5 volts and have a gain of .8, so that I end up with a line level sine wave.

Thus I am trying to design a single supply op amp with the following equation:

$$V_{\text{o}} = (V_{\text{i}}-2.5) \times 0.8$$

I found this white paper that is supposed to describe a way to do this but I'm having trouble following as I am new to op-amps.

https://www.eecs.umich.edu/courses/eecs452/Labs/circuit4.pdf

Does anyone know of a way to do this with a single op amp or IC?

The frequency range of 20Hz to 20KHz must be preserved.

Best Answer

You have the following situation:

Arduino with DAC generates 0V - +5V sin wave (2.5V +/- 2.5V).

The output should be -2V - +2V sin wave (0V +/- 2V).

POSSIBLE SOLUTIONS:

solution #1:

Arduino with DAC + C1 + R1 + R2 (all elements are in series).

  • C1 + R, where R = R1 + R2 is a high pass filter
  • R1 and R2 is a voltage divider with the gain of 0.8 V/V
  • can be used if DAC is able to source/sink enough current

.

solution #2:

Arduino with DAC + opamp buffer + C1 + R1 + R2 (all elements are in series).

  • use in case your DAC is not able to source/sink enough current

.

solution #3: Arduino with DAC + opamp subtractor + C1 + R1 (all elements are in series).

  • C1 + R1 is a high pass filter

A single opamp in a configuration of the subtractor takes care of your equation:

Vo = (Vi-2.5) * 0.8

subtractor

Look here: http://www.mtcmos.com/subtractor/ . You would like to use the configuration at the end of the article, that is, the left from this picture:

the solution

You set:

  • R2/R1 = 0.8
  • V1 = 2.5V
  • V2 = Vi

So you get:

Vo = 0.8 * (Vi - 2.5)

You may also refer to this e-book https://payhip.com/b/5Srt. The subtractor circuit explanation is a bit improved there (the core is the same), but you also find other configurations explained.

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