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OPA172: Single-Supply, Electret Microphone Pre-Amplifier Reference Design for OPA172

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Part Number: OPA172

Dear,

our client design opa172 as attached, but wavefrom was something wrong.

opa172.pdf

have any suggstion, if any question.

Please advise me.

Thanks,

Best regards,

Lawrence.

reference:

TI Designs – Precision: Verified Design
Single-Supply, Electret Microphone Pre-Amplifier
Reference Design

  • Lawrence,

    Assuming headphone is a 32 ohm load. there will be more voltage loss across R70 and C73. Xc=1/(6.28*2.2uF*1kHz)= 72 ohms.
    Headphone voltage will be 3Vpp * 32 ohms / ( 32 ohms + 50 ohms + 72i ohms)
    3Vpp * 32 ohms / ( 82 ohms + 72i ohms)
    3Vpp * 32 ohms / sqrt ( 82^2+ 72^2) ohms
    0.88Vpp ; this is close to actual green signal, so problem identified.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

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