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OPA692: 1:4 video buffer amplifier request

Jonathan Geronga
Expert 7930 points
Part Number: OPA692
Other Parts Discussed in Thread: LMH6321

Hi Team,

Do you have a better solution for the customer request for 1:4 video buffer amplifier for a single input (5v analog signal) to 4 identical outputs (four 5V analog signals) of the input signal, capable of driving Rload (1K ohm each).

Input signal: 5V
Output signal: 5V;

Thanks,

Jonathan

 

  • 0
    Guru 140200 points

    Hi Jonathan,

    what is the exact value of your input signal? What do you mean by "5V"? RMS or Vpp or Vp?

    And what do you mean by "1k pull-down resistor"? Just a simple 1k load resistance?

    Kai

  • 0 in reply to kai klaas69
    TI__Expert 7930 points

    Hi Kai,

    The input signal is a 5V Vp only.


    Let me know if we have a better offering.

    Regards,

    Jonathan 

  • 0 in reply to Jonathan Geronga
    Guru 48395 points

    Well Jonathan

    Topologically, your request is making little sense thus far, you are going 1 to 4 then 4 to 1 in the ADI mux. Why?

    At an implementation level, assuming something like this will emerge, you always need to consider the input C of those mux's, that will lead to a series iso R to the mux, with some insertion loss. Then, what is on the other side of the mux, 100ohm load will give a different need than 1Mohm load. Here are those mux cap specs. 

  • 0 in reply to Jonathan Geronga
    TI__Genius 15555 points

    Hello Jonathan, 

    Just to confirm each load is set to 1kohms here rather than the 75-ohms shown in the first image, correct? What supplies are being used here?

    Best,

    Hasan Babiker

  • 0 in reply to Hasan Babiker31
    TI__Expert 7930 points

    Hi Hasan and Michael,

    Yes, 1K ohm is being used as the load here. The 1K ohm is used as a soft pull down when there is no signal present on (s1) of ADG5404FBRUZ.
    The power supplies they are using for ADG5404FBRUZ  is (+/- ) 5V.
    Power supplies for the op-amp can be anything to get the job done.

    This is the information I get from the customer.

    Please let me know if the above information is enough for us to offer a suitable TI part for the customer.

    The customer is okay for 1:2 or 1:3 if there's no available 1:4 solution.

    Regards,

    Jonathan

  • 0 in reply to Jonathan Geronga
    TI__Genius 15555 points

    Hello Jonathan,

    The LMH6321 may be a better option here as it is more capable in driving capacitive loads. You didn't mention which supplies were being used, be sure to confirm that you aren't exceeding your output swing conditions. Note that if an isolation resistor is needed to stabilize the circuit there will be some attenuation loss which will vary based on the load past the MUX as Michael mentioned. 

    Best,

    Hasan Babiker