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LMH32401: How to connect negative voltage and APD with LMH32401

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Replies: 9

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Part Number: LMH32401

Dear Sir,

How could I connect LMH32401 with a negative voltage and APD.  Is the below circuit OK?  The (Out+)- (Out-) is in accordance with the APD current, right?

And could you please give me some guidance(with picture) if my connection is wrong?

Best Regards,
Helen

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9 Replies

  • Hello Helen,

    Below is the photo-diode configuration as shown in the datasheet:

    You should not connect ground to the input pin. The LMH32401 will provide a positive bias of around 2.5V.

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Thanks Hasan,

    What about the below connection , is it OK?  What is the right connection if the below circuit is still wrong? Could you please show me by picture?

    Best Regards,
    Helen

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  • In reply to Helen chen:

    Hello Helen, 

    Yes this should work. Not sure of the photodiode you are using here, but the 10k resistor may limit the input current of your circuit.

    Best,

    Hasan Babiker 

  • In reply to Hasan Babiker31:

    Thank you for the update Hasan.

    One more question, what kind of APD you used in your test? Could you please share the APD part number(around  -60V - -90V rating ) and the  resistor value with us? We want to promote our negative boost solution to our customer.  But we lack of the APD application knowledge.

    Thanks again.

    Best Regards,
    Helen

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  • In reply to Helen chen:

    Hello Helen,

    To clarify, I think it'd be better to not include the 10k resistor so you can get the full performance of the photodiode. Outside of the promoting the boosting feature are there any requirements for this photodiode? Are you looking for a fiber connected or open type photodiode?

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Hi Hasan,

    The information we got is -60V/10mA or -90V/2mA photo diode.

    I have no idea of fiber connected or open type photo diode,  any difference?

    Best Regards,
    Helen

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  • In reply to Helen chen:

    Hello Helen,

    The difference is how you plan on providing light to the photodiode. For an open-type, you can just shine a light on the device vs. with a fiber-connected photodiode you would typically connect to a laser diode through a fiber connector. 

    You can see the difference here (unmounted vs. pigtailed).

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Thanks for the information, its interesting.

    I want to use an open-type photodiode in my application.  Do you have some part number to recommend to us? :) It will be helpful to us.

    Best Regards,
    Helen

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  • In reply to Helen chen:

    Hello Helen,

    Options will vary based on specifications of your light source. Hamamatsu and first sensor should have a lot of options that you can take a look at.

    Best,

    Hasan Babiker

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