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    Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    What is the difference between the Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold Amplifier ?

    Is Bandwidth in tracking mode different then the sampling bandwidth ?

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    Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    Depends how you like to define bandwidth.

    Small signal bandwidth as -3dB from flat-top, is not
    a very useful descriptor of a T/H amp's performance
    when what you care about is a settled-to-N-bits
    time window. And T/H amp intra-cycle performance
    is neither continuous-time nor small signal - it's
    clocked, discontinuous and dealing with switch charge
    injection on top of natural amplifier settling.

    I'm no ADC specialist but you need way more BW
    to get decent THA - ADC lineup performance than
    your sampling clock frequency. Off the cuff I'd call
    it fClk*2^N or something like that - figuring T/H amp
    is a capacitor burdened unity gain follower, and you
    want about 1/2^N gain error @ freq.



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    Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    Sampling bandwidth is defined by the Nyquist criteria, i.e. the sampling frequency must be greater than twice the highest signal frequency of interest to reconstruct the waveform (in practice a significantly higher sample frequency than the minimum is usually used to allow analog low-pass filtering of the signal to minimize aliased noise).

    In the track mode you want a bandwidth sufficient so that it can settle to the desired precision within the sample acquisition time.
    That bandwidth is usually higher than the sampling bandwidth.
    Zapper
    Curmudgeon Elektroniker



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    Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    Crutschow,

    Thank you for your answer.

    So the sampling bandwidth is the max sinuosoidal bandwidth that can be sampled while the tracking bandwidth is the maximum sinuosidal bandwidth that can be acquired and tracked to the desired precision. But why would you want a higher tracking bandwidth if you can''t sample it ? You just would just a higher clock frequency to increase the sampling bandwidth since it can acquire and track the signal ?



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    Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    Hi,

    But why would you want a higher tracking bandwidth if you can''t sample it
    Undersampling...

    Many RF systems use undersampling technique.
    If interested: do an internet search.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: Sampling Bandwidth vs. Bandwidth in Tracking Mode of a Sample/Track and Hold

    I doubt that both terms have clearly commonly understood definitions. The original post is apparently referring to a paper or datasheet. If so, why don't you quote the definition therin.

    tracking bandwidth is the maximum sinuosidal bandwidth that can be acquired and tracked to the desired precision
    It's more commonly understood as -3dB bandwidth in tracking mode, I think. Small and large signal behavior has to distinguished.

    I agree that sampling bandwidth can be reasonably read as Nyquist frequency, as suggested by crutschow. But the term could also describe the aperture bandwidth of a sampler. For clarity, I suggest to desribe a test setup and how the respective parameters are derived.



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