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Thread: Howto: simple Differential Amp + TTL ?

  1. #11
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    You're completely correct. In post #8 I realized that you were right when I took a closer look and compared both schematics (this one and the original Dean Hammonds schematic).

  2. #12
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    Quote Originally Posted by dave View Post
    lazy option - use a Burr Brown DRV134
    I like the Idea. How i use the Chip?
    On the Vsup/Swing Graph its linear, so when i supply it with ±5V it will output 10V p-p?
    And the Offset, can it be set in the IC or have to be buffered/nulled externally?


    About the wrong OPA use Thing:

    This is the original Design by Nicolay (weartronics) i hope i may reupload it here:

  3. #13
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    weartronics is at least 10X more knowledgeable about electronics than I am.. if that's what he says, that's what I'd do. That's all I'll say. Perhaps he'll see this thread and give us his $.02.

  4. #14
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    Yes i hope this too. I should ask him about the Buffer thing... im not sure if it will still work when i change the Supply to ±12 V instead of the ±5V in his plans

    i played with Multisim and the DRV134 a bit, but i think im going it wrong. Clipping here and there...

  5. #15
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    Quote Originally Posted by ElektroFreak View Post
    weartronics is at least 10X more knowledgeable about electronics than I am.. if that's what he says, that's what I'd do. That's all I'll say. Perhaps he'll see this thread and give us his $.02.
    I had a second look and the amplifier WILL work, if you treat it as a non-inverting type (with Voffset acting as ground). That's great if you need a fixed amount of gain, but an inverting amplfier is a little easier to build and allows for some more flexibility when adjusting your gain. Both work, whatever floats your boat, I guess.

  6. #16
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    Quote Originally Posted by Stoney3K View Post
    That's great if you need a fixed amount of gain, but an inverting amplfier is a little easier to build and allows for some more flexibility when adjusting your gain. Both work, whatever floats your boat, I guess.
    I would like an adjustable gain (with fixed offset). Just tell me how to do it Symmetrical (Differential)

  7. #17
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    Well...

    Im simulating weartronic's Circuti now, but it works "50%" only
    The Vref Spurce gives stable 2.25 like it should.
    And the first OpAmp really amplifies

    But the second one gives not a symmetrical negative signal, instead just an negative offest to the + one!

    any clue?
    Attached Thumbnails Attached Thumbnails weartronicssim1j0wo.png  


  8. #18
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    Quote Originally Posted by Xer0 View Post
    Well...

    Im simulating weartronic's Circuti now, but it works "50%" only
    The Vref Spurce gives stable 2.25 like it should.
    And the first OpAmp really amplifies

    But the second one gives not a symmetrical negative signal, instead just an negative offest to the + one!

    any clue?
    The second opamp in the sim screen capture is NOT powered, see the Xs on the power leads? Sometimes the folks who create chip models do not always carry the power signals to where they should be, and this can cause a mess in the simulation code, because it does not have a proper bias on the device.
    correct that and run it again and show us the waveforms.

    Steve
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    When I still could have...

  9. #19
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    Quote Originally Posted by Xer0 View Post
    Well...

    Im simulating weartronic's Circuti now, but it works "50%" only
    The Vref Spurce gives stable 2.25 like it should.
    And the first OpAmp really amplifies

    But the second one gives not a symmetrical negative signal, instead just an negative offest to the + one!

    any clue?
    The second opamp in the sim is NOT powered, see the Xs on the power leads? Sometimes the folks who create chip models do not always carry the power signals to where they should be, and this can cause a mess in the simulation code, because it does not have a proper bias on the device.
    correct that and run it again and show us the waveforms. Without the power its gonna act as a mess of diodes, and perhaps clip like your drawing shows..

    Also you don't need R6-100 ohms in series with the 47K.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  10. #20
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    OK i put a new TL072 at the other ones place and rewired the connections bevore/after R6 correctly

    but its still not what i need...
    Attached Thumbnails Attached Thumbnails weartronicssim2q0my.png  


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