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There is a galvo-mirror which needs the following analog inputs:

enter image description here

DAQ boards are expensive and seems overkill to me.

I can live with 12-bit so I was planning to use a microcontroller board which has two 12-bit DACs with 0V-3.3V range. But I can only create diff signals as shown on the left below. But I need the signals as shown the right side below:

enter image description here

So I both need voltage amplification and bipolar outputs from my micro's outputs. What should I look for as specs and device in such a case? Only fully diff amplifier came to my mind after a quick search. Can that be the correct approach to handle this problem? And I tried to find a fully diff amplifier and couldn't find anything in DIP package which I can only solder.

edit for a comment:

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edit 2: enter image description here

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  • \$\begingroup\$ My problem is I cannot find such a diff amplifier with bipolar outputs. Here is all I got uk.rs-online.com/web/c/semiconductors/amplifiers-comparators/… \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 9:40
  • \$\begingroup\$ Ok. Sorry. I did not "read" at the end. Will search. \$\endgroup\$
    – Antonio51
    Commented Feb 11, 2022 at 9:43
  • \$\begingroup\$ And regarding 3.2 I dont necessarily need SE to DE conversion. Since I can create diff ended signals by micro. But I need to amplify them and bipolar outputs as I show in my question. \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 9:43
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    \$\begingroup\$ Fully differential amplifier means an amplifier which has differential input and differential output. It has nothing to do with bipolar output, i.e. setting the common mode of the differential output to 0V. You can just use one DAC output channel, and change the DC bias, gain, and provide bipolar differential output with standard op-amps, you only need positive and negative supply voltage for op-amps. \$\endgroup\$
    – Justme
    Commented Feb 11, 2022 at 9:44
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    \$\begingroup\$ There is a galvo-mirror which needs the following analog inputs: - then don't state what an undesirable DAQ solution might be; state what is needed for the device. \$\endgroup\$
    – Andy aka
    Commented Feb 11, 2022 at 11:31

2 Answers 2

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schematic

simulate this circuit – Schematic created using CircuitLab

Maybe something like this, maybe $1 worth of parts. The op-amp will need something like +/-15VDC supplies.

This assumes something like the Thor Labs GSV series, which have 20K input impedance.

Differential output voltage is -20V for Vin = 0, 0V for Vin = 1.65V and +20V for Vin = 3.3V.

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  • \$\begingroup\$ Thanks! I simulated this in LTspice as well it outputs as expected. What does Vp indicate? And this is done to reject noise for the galvo mirror correct? \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 10:56
  • \$\begingroup\$ Vp is just a net name to indicate it's the 3.3V rail. It should reject smallish common-mode noise. You can use a better op-amp than an LM324 but I'm not sure it's necessary. Noise on the 3.3V rail (and DAC output) may be more of a limitation. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Feb 11, 2022 at 10:58
  • \$\begingroup\$ I was using two DACs as differential output in my question. So in your circuit if the inputs were also diff ended that would be les sn oisy I guess? \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 11:03
  • \$\begingroup\$ I don't think so. The noise is likely primarily from the power supply so one or two will be similarly noisy. If noise is an issue in practice, consider using a DAC chip with a precision reference and interfacing it with I2C or whatever. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Feb 11, 2022 at 11:04
  • \$\begingroup\$ Hi again, I simulated your circuit in LTspice works very fine in sim. And I wanted to create 0/+10V and 0/-10V outputs from 0/3.3V input. For that I removed Vp and grounded that input; and used 30k resistors instead of 60.6k like here: i.sstatic.net/a6VRZ.png I get what I want in the simulation i.sstatic.net/Due84.png. But wanted to have your opinion. Do you think it is fine to do this? \$\endgroup\$
    – user1999
    Commented Feb 14, 2022 at 17:02
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Something as this?
Based on the first stage full "instrumentation amplifier"

enter image description here

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  • \$\begingroup\$ This also works like other answer in LTspice with LM324 in simualtion. Do you think LM324 suffice? \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 12:56
  • \$\begingroup\$ @user1999 Note that LM324 is a quad. opamp. (4 opamps in one IC). There are dual opamp alternatives if you decide to go with this circuit. Also, check Andy's comment on the question. There may be issues which are important and could change the recommended solution. \$\endgroup\$
    – devnull
    Commented Feb 11, 2022 at 13:04
  • \$\begingroup\$ I want to try both answers. To control the galvo two analog inputs needed. My micro has two DACs. So going for the other answer I can use one micro board for one galvo. This answer uses two DAC for one galvo(meaning I need two micro board) input but this can reject noise more that the other. Very curious about the results. \$\endgroup\$
    – user1999
    Commented Feb 11, 2022 at 13:08

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