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ONET4201PA: ONET4201PA input connect

user5880333
Prodigy 20 points
Part Number: ONET4201PA
Other Parts Discussed in Thread: OPA855, , ONET8551T

We use PD+OPA855+ONET4201PA to  achieve optical wireless communication，OPA855 is single-ended output，How can OPA855 output connect to ONET4201PA? thanks.

  • 0
    TI__Mastermind 28628 points

    Hi,

    Do you know the expected electrical characteristics of the output from the OPA855 in your application?  What is the expected swing?  What data rate will you be operating at?

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 20 points

    Hi Drew Miller1, thank you for  your reply. The power of OPA855 is 3.3V, So the opa855 output range is 1.05V~2.4V， the data rate is about 200Mbps.

  • +1 in reply to user5880333
    TI__Mastermind 28628 points

    Hi,

    Have you considered using a dedicated TIA+Limiting Amplifier device such as ONET8551T?  I'm wondering if a device like this would simplify your design.

    Regarding your current design, the ONET4201PA has a maximum recommended input voltage of 1200mVppd.  For a single ended signal, I would recommend an amplitude of 600mVpp.  Given that the expected output range is ~1.4Vpp, I would consider using a T-network attenuator in order to reduce the amplitude to <600mVpp.

    Inputs to the ONET4201PA should be AC coupled.  The output of the T-network could be connected through an AC coupling capacitor to DIN+.  Regarding the unused input (DIN-), it can be connected to GND through a 50 Ohm resistor and AC coupling capacitor (DIN- --> AC Coupling Cap --> 50 Ohm R --> GND).

    Please let us know if you have follow up questions.

    Thanks,
    Drew

  • 0 in reply to Drew Miller1
    Prodigy 20 points

    Hi Drew Miller1, thank you for  your reply. ONET8551T is die and not convenient to use, I'm not sure it can operate to frequency of 200MHz.