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OPA361Q1 input attenuation network

Michael Huang3
Intellectual 2460 points

Hi all,

My customer use OPA361Q1 and want it just as a buffer, 1:1. So I want to add a 2k resistor in serial with the inside input resistor 500ohm, and be a 1/5 attenuation. and then the total gain is 1:1

Another question is if we can just leave RSET disconnect? in older post, I see a same question post to ask RSET. I think it is OK, right? the output impendance of source is 75ohm.

Regards

Michael 

  • 0
    TI__Genius 13935 points

    Hello Michael,

    It would be better to build a PI attenuator that would preserve the impedance of the signal path.  Using a series resistor will put a mismatch of impedance at the amplifier input.  


    You can calculate your resistor values here:

    http://chemandy.com/calculators/matching-pi-attenuator-calculator.htm

    I do not know what the Rset is for.  It looks like it is used to interface to a different part and has no function for the Amplifier. 

    Loren

  • 0 in reply to Loren Siebert 1
    TI__Intellectual 2460 points

    Hi Loren,

    Thanks for your reply. and kindly give me the web to calculate the PI network.

    I wonder what issue will happen because of the mismatch. Because it is not a very high frequency and there's no long cable here, just some centimeter pcb trace.

    Because the things i learned before for mismatch, we always referred to Gbps, MHz. So i don't know what will happen to the mismatch here.

    Thanks

    Michael