Lm331 output problem

Discussion in 'General Electronics Chat' started by hasanferoz, Mar 28, 2011.

  1. hasanferoz

    Thread Starter New Member

    Mar 8, 2011
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    I CANT GET A STABLE OUTPUT PLEASE HELP ckt is attached frquency keeps on changing
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you have bypass capacitors connected across the V+ and GND terminals, as close as possible to the IC? I suggest an 0.1uF ceramic or metal poly film and a 1uF or larger aluminum electrolytic capacitor.

    Do you have a good ground plane, or is this wired up on a breadboard? A breadboarded circuit could have a lot of problems due to the length of wires, etc.

    You should show your circuit layout. It is difficult to get a good photo of circuits. The best lighting is outside on an overcast (cloudy) day.
     
  3. hasanferoz

    Thread Starter New Member

    Mar 8, 2011
    25
    0
    i have soldered da circuit yup i have placed by passed capacitors
     
  4. hasanferoz

    Thread Starter New Member

    Mar 8, 2011
    25
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    hey i found this ckt in an application note and there is a difference between the ckt impletemented at 1 and 6 i have circle the portion can anyone tell me whthere this could be the problem
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Why don't you contact the manufacturer about this problem?
    They have engineers available to help you with their products.
    I am not familiar with the LM331, I don't have any available, and very little time to attempt a remedy.

    I suspect that you may have some kind of ground-related problem that is causing your output frequency to change. It could also be caused by other electrical/electronic equipment nearby, generating EMI/RFI, that could cause circuit instability.

    Try enclosing your circuit in a conductive box and connecting the box to earth ground.

    You are giving very little information, and somehow expect us to magically produce an answer for you to save your job. Most of us on the forums are hobbyists; doing this for fun.
     
    hasanferoz likes this.
  6. hasanferoz

    Thread Starter New Member

    Mar 8, 2011
    25
    0
    well wat other info do i need to give i have just found a conflict which i told u anyways thanx for all ur replies ill try awl ur suggestions
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Document everything.
    Part numbers and vendors that you used, for all of the parts, including the LM331.
    If the vendor for the LM331 was not an authorized distributor, you may have a counterfeit LM331.
    Document the exact layout that you used. Clear, in-focus photographs preferred.
    Document the exact circuit you used.
    Document your input voltages used, and the output frequencies, or range of frequencies observed, along with the expected frequencies and range of frequencies.
     
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