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Unusual application for ONET4251PA

Stephen Robertson1
Prodigy 20 points
Other Parts Discussed in Thread: ONET4251PA

Hi everyone,

I'm an analog/RF engineer working at Anritsu Company, in Morgan Hill, CA.

I am thinking about usint the ONET4251PA as a log-amp with differential outputs.  I need HUGE amounts of gain for CW signals at frequencies as low as 10kHz.  I am trying to design a signal canceller with 160dBc of cancellation!  The dynamic range is just as big.  The canceller must be able to handle signal levels from 0dBm to minus 160dBm.  To accomplish this, I am basically designing a radio with multiple IF gain stages, each of which has progressively narrower bandwidth.  Four successive stages would do the job.

I realize this is not how the ONET4251PA is typcally used, but I suspect, after having read the datasheet several times, it can do the job with careful attention to input noise.  I would love to speak with a TI engineer familiar with this part.  I have specific questions related to noise, input hysteresis, low-frequency operation, and polarity control.

  • 0
    TI__Expert 8915 points

    Hello Stephen.

    For your application you need a much narrower band amplifier. The ONET4251PA is a wideband amplfier from kHz range to GHz range so the noise will be too high. For -160dBm input signal you need much lower noise than this amplifier. -160dBm translates to a differential input signal of around 9nV. This amplifier will not detect this signal at all. The 4251PA should have inputs above about -50dBm (3mVpp differential).

    Also, at signal inputs about 3mVpp, the amplitude is limited and will create a lot of harmonic content which is probably not good for you signal canceller.

    Regards,

    Alex.

  • 0 in reply to Alex Davidson
    Prodigy 20 points

    Hi Alex,

    See attached block diagram.  Aware of broadband considerations.  Need information not in datasheet like:

    input related noise in dB/root-Hz?

    maximum rate OUTPOL pin can switch at?  Can it be switched at an 11MHz rate?

    any hysteresis?

    Please call me at 408-201-1370  9-5 pst.

    Thanks,

    Stephen "Andy" Robertson

  • 0 in reply to Stephen Robertson1
    TI__Expert 8915 points

    Andy,

    I will call you.

    Alex.