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LMP8350: Reference design

yuki-kubo
Prodigy 30 points
Part Number: LMP8350

Fig 34 of the datasheet has a circuit example of single-ended input/differential output, but if the input (VI) is an OPAMP output, are Rs and Rt necessary?

Please let me know the recommended resistance values (Rs, Rt, RM) if necessary.

What is the recommended resistance value (Rg, Rf) that determines the gain? (100Ω to 1kΩ or 1kΩ to 10kΩ or 10kΩ to 100kΩ)

  • +1
    TI__Intellectual 1080 points

    Hello,

    Thank you for your question. The resistor values around the FDA are going to be determined by the input and source resistance values. Attached and linked here (TI FDA Calculator) is a calculator that will help you determine the proper values for Rs, Rt, and RM based on your input conditions. 

    Average values for Rf and Rg would be around 1kΩ for Rf and between 500Ω to 1kΩ for Rg. These values are variable however and can be changed based on your desired gain as well as these values help determine the other resistor values. In general, the higher the resistor value, the larger the power dissipation and resistor noise. Please use the calculator to help determine the proper settings around the FDA. 

    These resistor values are important to ensure that both inputs to the FDA are symmetrical to get the best distortion and CMRR performance. It is also important to ensure that proper impedance matching practices are taken to help prevent any reflections of the high frequency signal. 

    TI FDA Calculator.xlsm

    Thank you,
    Rachel