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Unable to get current

Discussion in 'Circuit Simulation & PCB Design' started by momo36, Nov 4, 2016.

  1. momo36

    momo36 New Member

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    hi, i would like to habe current from 3 bit . the first bit 40 microA, second bit 20microA and the last bit 10microA. Attached is my circuit design but i am unable to get the current as required. Any want able to help?
     

    Attached Files:

  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi
    I get missing models errors with the asc files.
    This image shows that the VOUT label is NOT connected.
    E
     

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    • A10.gif
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  3. momo36

    momo36 New Member

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    but it can openly fine from mine.
    upload_2016-11-5_8-33-47.png
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi 36,
    I have tried again, downloaded all your files, still cannot get it to open, missing model error.

    Look a this image, move the VOUT label on your circuit so it is the same as image, else it is NOT connected.

    E
     

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  6. spec

    spec Well-Known Member Most Helpful Member

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    Hi momo,

    What DAC are you using?

    If you want to sum currents and produce a corresponding voltage out put (so that you can measure the total current), the usual way is to use a current-summing, virtual-earth amplifier (transimpedance amplifier). The transfer function is Vout = -Iin* R23.

    UPDATE: The current inputs to the circuit below are the current outputs from the DACs (should be 3 not 4 as shown).


    2016_11_05_Iss1_ETO_CURRENT_SUMMING_AMP_VER1.png


     
    Last edited: Nov 7, 2016
  7. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi 36,
    I have combined and redrawn your asc file, it now runs for me.
    Is the image showing the result you are expecting.?
    E
     

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  8. momo36

    momo36 New Member

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    hi ericgibbs,

    thanks for ur help. i would like to have current where bit 1 40micro second bit 20 micro and third bit 10 micro
     
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Hi,
    Do you mean like this plot.?
    E
     

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  10. momo36

    momo36 New Member

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    i mean bit one has current of 40 microA, bit 2 has current of 20 micro A and bit 3 has current of 10 micro ampere
     
  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    You did say 40micro second.
    I will look at the problem later.

    You may find this option for setting the Bits useful for testing, Set the Bits by using the SW SET = 1 or 0

    E
     

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  12. momo36

    momo36 New Member

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    sorry. wanted current :)
     
  13. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Which node/component of the circuit are you wanting to measure the current thru.?
     
  14. momo36

    momo36 New Member

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    i wanted to measure the Iout current for bit 1 bit 2 and bit 3
     
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    You have 3 identical circuits, as drawn each circuit is able to source a current of ~ 50uA
    The only parameter that will change with different Bit patterns is Vout.

    Is this a College assignment or an actual circuit you are designing.
    E
     

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  16. momo36

    momo36 New Member

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    it is actual circuit design
     
  17. eTech

    eTech Active Member

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    Hi

    Mouse over each output wire (the cursor will change to a current probe icon), then press ALT-Click.
    The measurement will display in the waveform pane.

    Or

    You can use a voltage source as a current meter. Place it in series with each output wire and set its value to zero.
    Then mouse over the voltage source and click. The measurement will display in the waveform pane

    I changed the trans time to 10uS. I also dded wire labels to example B for clarity.

    See attached.
     

    Attached Files:

    Last edited: Nov 7, 2016
  18. eTech

    eTech Active Member

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    Open the Switchable_Current_Source.asc file. Then from the Hierarchy menu, select "Open this sheets symbol".
    The symbol will be auto created and placed in the current folder.
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi 36,
    This is one option to get a 10uA,20uA,40uA current for 3 Bits.
    Note I have labelled the Bit's MSB,Bit1,LSB.
    E
     

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  20. momo36

    momo36 New Member

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    h. thanks. can you foward me the real scematic
     
  21. momo36

    momo36 New Member

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    upload_2016-11-8_17-32-26.png

    what is this for ? the purpose and function of it?
     

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