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ONET85xx series TIA for 1 pF APD

Eric Harmon80
Prodigy 10 points
Other Parts Discussed in Thread: ONET8521T, ONET8551T

I have an application requiring 2.5 GHz operation of an avalanche photodiode.  The APD has a capacitance of about 1 pF and operates at a bias voltage of 50V.  I would like to use the ONET85xx series for this device (wire bonded in a TO can).

Is there any data as to how the ONET85xx series works with varying capacitance (the data sheet specifies 0.2 pF capacitance)?  Are there any suitable SPICE or TINA models that can be used to predict performance (particularly with respect to capacitance and bond wire inductance).

Thanks,

Eric

  • 0
    TI__Expert 8915 points

    Hello Eric,

    Since the bandwidth of a TIA is inversely proportional to the total input capacitance (TIA input capacitance + photodiode capacitance), the large PD capacitance can reduce the BW by up to 5 times the typical value. However, it will also impact the sensitivity. For optimal noise performance the parts are designed to have a low capacitance input, in fact, the TIA input capacitance should equal the PD capacitance for optimal performance.

    For APD applications in a TO can I recommend the ONET8521T or ONET8551T only. An s-parameter model for the ONET8521T is available on the TI website and if you provide me with your email address I can send you an IBIS-AMI model of the ONET8551T. We do not have SPICE or TINA models available.

    Regards,

    Alex.