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LMH6551 AC coupling

Sachin Munjpara
Intellectual 290 points

Other Parts Discussed in Thread: LMH6551

Hi Everyone,

I am using LMH6551 to drive an ADC. ADC is providing common mode voltage of 0.9V to op-amp. I have DC coupled differential analog signals to op-amp. The common mode voltage of analog signals is 1.5V. In datasheet of op-amp it is not mentioned whether the input should be AC coupled or not. But it looks like it should be. Can anyone guide me whether I should AC couple the signals or I can keep them DC coupled?

Thanks,

Sachin

  • 0
    TI__Mastermind 22825 points

    Hi Sachin,

    The LMH6551 can be DC or AC coupled. You just have to make sure the Input CM voltage (Vi_CM) range is not violated (i.e. stay within -4.6V to +3.1V with +/-5V supplies):

    The 1.5V of your analog input, along with the ADC CM voltage and the gain setting will impact this:

    Vi_CM= 1.5V * (RF / (RF+RG)) + 0.9V * (RG / (RF + RG))

    For RF = RG : Vi_CM = 1.2V

    Please let me know if you need additional information?

    Regards,

    Hooman