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Original question:

THS4567: THS4567 TINA reference design has some oddities in default circuit

THS4567: Measures gain/phase characteristics

Hiroaki Yuyama TED
Expert 1560 points
Part Number: THS4567

Dear, Support Team.

Our customer uses a transimpedance to drive the photodirector current to a differential voltage output.
However, the customer seems to have an oscillating output.
Please tell me how to measure the gain/phase characteristics of the transimpedance circuit of the THS4567 for differential output.


The differential output is AC coupled.
Common mode voltage may fluctuate.
Does the capacitance of the coupling capacitor have any effect?

THS4567 differential output is AC coupled.pptx

Best Regards,
Hiroaki Yuyama

  • 0
    TI__Expert 6050 points

    Hi Hiroaki,

    I looked at the attachment you provided, but the circuit was very small and blurry so I am not able to reproduce it from that image. Would you be able to provide a clearer image or attach a schematic file if you have that? I will be able to assist further with that.

    Thanks,

    Nick

  • 0 in reply to Nick Nauman
    Expert 1560 points

    Hello Nick-san.

    Our customer's circuit has not been publicly disclosed.
    Please let me know how to measure the phase margin so that the customer can continue to evaluate.

    Best Regards,
    Hiroaki Yuyama



  • 0 in reply to Hiroaki Yuyama TED
    TI__Expert 6050 points

    Hi Hiroaki-san,

    I completely understand. Just to confirm, are you running the THS4567 in Differential TIA mode with the ICM loop enabled (ICM_EN = 2.5V)?

    The following resources should help you understand how to evaluate the phase margin:

    TI Precision Labs Op Amps Video Series -> This video series has a section covering stability. There is also a video covering stability of FDAs in the corresponding section

    TIA Blog Series -> This blog covers stability analysis of TIA circuits

    Stability Analysis Article -> This is an in-depth article covering stability analysis

    Please let me know if there are still any questions.

    Thanks,

    Nick