Strange

Discussion in 'General Electronics Chat' started by assassinelec, Apr 6, 2011.

  1. assassinelec

    Thread Starter New Member

    Mar 22, 2011
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    hi all, i want to ask u guys about something very strange happen in an analog multiplier IC , i have an anlog multiplier IC it works as a modulator has two input signal the carrier signal and the information signal and the output is modulation of them , when i connected the output to an oscilloscope i did't see any thing just random noise , but the strange thing when i accidentally connected the oscilloscope prob to the Vcc of the multiplier (+5v) the signal which appeared on the oscilloscope is the carrier signal !!! with the exact carrier frequency, how the carrier signal came out from the Vcc terminal or may be the IC is damaged ? (btw the IC has +5v ,-5v and ground pins) , i need an explanation plz :)
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,779
    932
    We will need a schematic before we can explain this failure mode of an integrated circuit.

    Please.
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Will that circuit show some fairly large capacitors across the supply rails and ground? Lack of adequate supply decoupling capacitors could lead to poor performance, with significant signal amplitudes appearing on the supplies. See link: http://forum.allaboutcircuits.com/showthread.php?t=45583
     
  4. assassinelec

    Thread Starter New Member

    Mar 22, 2011
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    thanx for replying, i read the link and i think i connected the IC wrong because i did't use any external component for it, plz take a fast look on the circuit i used to connect the IC , in the datasheet page 11, but i think i should use the one in page 10...also do u think the IC is damaged?

    http://www.analog.com/static/imported-files/data_sheets/AD835.pdf
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    The IC may be damaged, there is only one way to tell for sure.

    Connect it correctly, with decoupling capacitors, and probe the output again.

    If you are getting proper output, then you are likely fine.

    Without seeing how you connected it incorrectly, we cant tell if you supplied power to a protected or unprotected output pin.
     
  6. assassinelec

    Thread Starter New Member

    Mar 22, 2011
    13
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    @retched thanx for replying, i just want to know one thing if the circuit i should use is the one in page 10 , so what is the ciruit in page 11 for ??
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    From the datasheet, page 11:
    This is why you saw the signal on the +5v line; you did not use the decoupling capacitors that are shown in figure 20.

    You MUST READ THE DATASHEET and follow the guidelines while using the product, or you will have poor results.

    You must use the decoupling capacitors as shown in Figure 20. As far as which figure to use, choose one - but make certain to use the capacitors.
     
  8. assassinelec

    Thread Starter New Member

    Mar 22, 2011
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    @SgtWookie , man u my hero !!! u have an answer for every problem i face :D
     
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