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OPA2134: OPA2134 noise issue and gain is not good.

user6154244
Prodigy 50 points
Part Number: OPA2134
Other Parts Discussed in Thread: OPA2365

Dear PIC

We have a issue that there is noise and gain is not good.

So it would be helpful if you could help us to resolve issue.

Please attached file.

OPA2134 question.xlsx

  • 0
    TI__Genius 10850 points

    Hello User6154244,

    Thank you for your post. Can you please help answer a few questions to help the analysis?

    • What is the expected input signal to the OPA2134? Amplitude and frequency of Sine wave?
    • What is the desired gain?
    • How are you measuring the performance? What instrument are you using?

    -Tamara

  • 0 in reply to Tamara M Alani
    Prodigy 50 points

    Dear Tamara-san,

    Thank you for your reply.
    This device is Audience rating measurement equipment and need to get TV sound.
    So need to get 100Hz - 4kHz.
    Also, in order to check the spec, we need to pass the test as below spec,
    And, we have another problem as below.
    In order to input 2Vrms, I think that Gain should be under 1 because Vcc is 5V.
    It would be hopeful if you could help us to resolve.
    At this time, we try to improve with 1.2Vrms,but these problem were occured.

    /***************Test Spec**************/
    Input level:2Vrms
    Input figure: Sine Wave
    Check point:100Hz,200Hz,500Hz,1kHz,2kHz,4kHz
    Judgement Criteria: Within ±3dB based on when 1kHz will be assumed as 0dB.

    /***************Test method**************/
    1)Input Sine Wave from Generator or PC
    2)Record pcm sound at NAND
    3)Get pcm sound from the device to PC.
    4)Analysis each frequency of sound.

  • 0 in reply to user6154244
    TI__Genius 10850 points

    Hello user,

    Thank you for the additional information. The OPA2134 has the following input common mode voltage range:

    So if you're operating at 5V single supply:

    • the minimum input voltage is (V-)+2.5 = 0+2.5 = 2.5V
    • the maximum input voltage is (V+)-2.5 = 5-2.5 = 2.5V

    So the input voltage range can only be 2.5V for linear operation. Your input of 2Vrms is beyond this limit so your op amp is not operating linearly and thus all specs are susceptible to erroneous values. 

    To learn more about input/output limitations, follow this short training video created by our team: 

    • Input and Output limitations - Part 1
    • Input and Output limitations - Part 2

    I would recommend increasing the supply voltage, if possible, and try the measurement again.

    -Tamara

  • 0 in reply to user6154244
    Genius 3945 points

    "In order to input 2Vrms, I think that Gain should be under 1 because Vcc is 5V."

    This part won't work (well) with a single 5V supply. Choose an op-amp that will, such as OPA2365.