Differential Op-Amp Circuit to translate +/-10V DAC signals from test equipment to 0-3.3V for Teensy 3.6 Board
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Finally got around to testing the op-amp section of the circuit. It works as advertised. The linearity is pretty good. :)
Following advice, I used the 3.3V as my bias voltage. Can't quite seem to get it down to 0V but this would work too with minimal additional components.
@K.C. Lee suggested using a resistor divider network with a bias voltage to scale and shift the +/- 10V to 0-3.3V. Duh! Why didn't I think of that? Added a LTSpice schematic and output plots of a circuit that gets the job done. I've already ordered the uber expensive LT op-amp, switched capacitance bipolar power supply, and linear regulator for the gen 1 design. Diligently pursuing sunk cost fallacy, I will build up and use the op-amp version for now. For the cost of a semi-precision 10V linear regulator and a few resistors I could've been down the road. Live and learn I guess. Thanks again @K.C. Lee!
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Ah. Didn't spend too much time analyzing the opamp.
BTW the 3.3V bias can be tied to the 3.3V supply from the Teensy assuming that's what used as the ADC reference source. The divider requires the antialias filter cap as it also lowers the AC impedance and supply charge to the... more
You might be able to do what I did here with just a couple of resistors:
https://cdn.hackaday.io/images/9954551466561935456.png
The resistor divider does the level shifting from +/- 3.3V to 0-3.3V. You can probably play around with divider values for +/-10V. I added a capacitor at the output to form a 1st order anti-alias filter for the 12-bit ADC in my STM32F030 in this project: https://hackaday.io/project/12133-automatic-audio-source-switching
It works very well. (I know you are using differential output.)
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@K.C. Lee, been thinking... I am actually not using a differential input signal. I'm actually bringing into two single ended inputs to the Teensy. The test machine DAC is outputting two unqiue channels, representing two different speeds,