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Original question:

LMH32401: if the -VBIAS of LMH32401 connect to GND directly, what will the negative bias be between Vin- and Vin+

LMH32401: Connect VIN with APD negative pin, is there any risk?

Shuang Feng76
Intellectual 2990 points
Part Number: LMH32401

due to my customer APD -VBIAS do not support negative voltage. they want to check whether LMH32401 could connect with APD negative pin to realize the function?

it seem our VIN will keep 2.47V VBIAS, because internal have this voltage.

will this work normally? or any risk?

about VOD voltage, we see there are two modes. could you help to explain the advantage of 0.4V mode? we just assume 0V mode, directly connect VOD with ground could work normally.

hope for your confirmation.

thanks a lot.

  • 0
    Guru 140200 points

    Hi Shuang,

    have you read section 7.3.2 of datasheet?

    Kai

  • 0
    TI__Expert 3620 points

    Hi Shuang, 

    I'm not sure I understand your question fully, but the LMH32401 is designed to work best with a negatively biased photodiode that sinks current.

    Operation with a photodiode that sources current will increase overdrive recovery time, which in severe cases can cause blind-spots in the system response.

    The VOD setting will directly effect the dynamic range of the output signal: 

    You can see that leaving VOD at 0V in this case does not make good use of the full output swing of the amplifier.

    As Kai suggested, these considerations are covered in-depth in the datasheet section 7.

    https://www.ti.com/lit/gpn/lmh32401

    Best,

    Sam