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THS4502: Differential Receiver for THS4502

joe lindula
Mastermind 6850 points
Part Number: THS4502
Other Parts Discussed in Thread: LMH6551, LMH6552, THS3215, VCA824, THS3217, VCA821, OPA820, LMH6609, OPA690, OPA847

Hello, I'm using the THS4502 as a Differential Line Driver. Can anyone recommend a Difference Line Receiver that will support the high-speed data rates of the THS4502? I'm using +5V/-5V voltage rails.

Thanks,

Joe

  • 0
    Mastermind 6850 points
    Oops, I should have said "Differential Line Receiver". My typo.
  • 0 in reply to joe lindula
    TI__Genius 15975 points
    Hi Joe,

    You could use the LMH6551 or LMH6552 for Differential Line Receiver application. They both support +5V/-5V voltage rails and should be able to support the THS4502 data rates.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Mastermind 6850 points
    Rohit,

    HI, thanks for the recommendation. I need to convert the Differential input to single-ended and is a voltage feedback amp. Can you recommend any devices that can support +5V/-5V voltage rails and support the THS4502 data rates or near those rates? I

    Thanks,
    Joe
  • 0 in reply to joe lindula
    TI__Genius 15975 points

    Hi Joe,

    I don't think we have a dedicated part for fixed gain Differential in and single-ended output in a voltage feedback amplifier configuration.

    You could use the THS3215 or THS3217 for converting Differential input to single-ended output, but it is a current-feedback amplifier. The VCA821 or VCA824 can also be used for Diff in to single-ended output and is a voltage feedback amplifier, but it is a variable gain part. It might be possible to tie the gain control pin to a fixed voltage and use in your application.  

    The other option is to build a difference amplifier at the output of THS4502 using voltage feedback amplifiers. The parts you can use for this is OPA690, OPA847, OPA820 or LMH6609.

    All the parts mentioned above should support the THS4502 data rates with +/-5V supply rails.

    Best Regards,

    Rohit 

  • 0 in reply to Rohit Bhat
    Mastermind 6850 points
    Thanks Rohit! I appreciate your time in helping me.
  • 0 in reply to joe lindula
    Mastermind 6850 points

    Rohit,

    HI, I have been looking at the VCA824 Variable Gain Amplifier and found on page 22 and example of a Difference Amplifier configuration. I have two questions that I hope can you help me find the answer to. First, how to pick Rg? Two, how to pick RS? Is there an equation for those resistors?

    Thanks,

    Joe

  • 0 in reply to joe lindula
    Mastermind 6850 points
    Oops, I forgot to mention that I am looking for a Gain of 1.
  • 0 in reply to joe lindula
    TI__Genius 15975 points

    Hi Joe,

    Setting up the RG is dependent upon the maximum current IRG flowing through this resistance  and should be less than +/-2.6 mA or 5.2mApp. I would recommend going through Section 8.4.1 on page 19 for this. 

    For a Gain of 1, I would recommend setting RF and RG to 453ohms and setting gain control pin VG to 0V. In this configuration, the max gain Avmax is set to 2V/V mainly governed by the below equation: Avmax = 2x(Rf/Rg).

    The main requirement to choose Rs is that the pole formed due to Rs and the parasitic input capacitance does not limit the bandwidth. This is given by the equation: 1/(2*pi*Rs*Cpar). 

    Best Regards,

    Rohit

  • 0 in reply to Rohit Bhat
    Mastermind 6850 points

    Thanks again!!