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LMH6882: GAIN PARAMETERS

Part Number: LMH6882

Hi team,

Do you mind me asking GAIN parameters? There are two figures, Figure 17 and Figure 19, in the LMH6882 datasheet, as shown below. Can you explain in detail what Gain Step Amplitude Error and Cumulative Amplitude Error mean? For example, in the first figure, what does the Gain Step Amplitude Error about -0.125dB mean when the VOLTAGE GAIN is 6dB? What does the Cumulative Amplitude Error mean in the second figure? Can you explain this with VOLTAGE GAIN 6dB as an example? I would like to know when I preset a voltage gain, the error depends on which figure.

Thanks,

Amy

  • Hi Amy,

    "gain step amplitude error" is the gain error of the "naked" gain cell, while "cumulative amplitude error" is the total gain error of the whole signal chain (including the gain cell)?

    Only a guess Relaxed

    Kai

  • Hi team,

    Can anyone give a more precise definition?

    Thanks,

    Amy

  • Hello Amy,

       I believe Kai is correct. Gain step amplitude error (Figure 17) refers to the amount of gain error between two adjacent steps. Cumulative amplitude error (Figure 19) refers to the amount of gain error between two adjacent steps added up from 6dB to 26dB. Let me confirm this with the validation team, and get back to you by tomorrow.

    Thank you,
    Sima

  • Hello Amy,

       I received confirmation that the earlier statements are correct. So you can use either figure, but I believe the most useful would be Figure 19.

    Thank you,

    Sima

  • Hi Sima,

    Thank you for your feedback, but I'm still confused, could you give an example of each of these two figures

  • Hello Amy,

      Figure 17 tells you the error between two steps, while Figure 19 tells you the error at that gain selection. So, if you choose voltage gain of 18dB you will see amplitude error of -0.05dB. You will notice in Figure 19 that the cumulative error at max gain is 0, because 26 dB or max gain is the reference point. But, Figure 17 tells you that the error between two adjacent gain error steps so for example the error between 17.75 and 18dB looks to be around -0.03dB. 

    An analogy for this would be to think of Figure 17 being a DNL plot and Figure 19 being an INL plot (not exactly, but similar to these DAC specifications).

    Thank you,

    Sima