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OPA1632: OPA1632 Gain resistor selection considertaion.

Part Number: OPA1632
Other Parts Discussed in Thread: TINA-TI

Hi Team,

My csutomer needs to recommandations on how to select the gain resistors for proper gain settings.

what informaiton does he need to provide, besides the gain which is easily calculated from the ration of the two resistor, for us to make suggestions?

  • Hello Andy,

      That is correct, the gain can be calculated through the ratio using the provided table. I would also recommending simulating the circuit with different gain configurations using the Pspice or Tina-TI model found here.  

        I would follow the diagram below for single to differential ended amplifiers when considering RF and RG values. This diagram takes into consideration of the impedance of the input source/signal generator. If disregarded, the FDA will vary in gains between the two outputs and degrade in performance such as in CMRR. 


      Also, for high speed amplifiers, it is important to impedance match at the input and output of the amplifier. This will minimize signal reflections at higher frequencies. However, this part seems to be on the lower end of our high speed amplifier parts, and is under audio applications. So, this is not a critical issue for signals in the kHz. 

      Here are very useful app notes we have that go over FDA configuration and explaining how critical it is to balance the FDA. 

    1) FDA PowerPoint (Above diagram found on slide 12)

    2) Impedance matching and balancing FDAs

    3) In Depth Input Impedance Matching FDAs

    4) In Depth Output Impedance Matching FDAs

    Thank you,