AD608 - What method is used for input offset auto nulling? Is the offset nulling loop a periodically updated (i.e. sampled) control loop or is it a continuous time control loop? If it is sampled, what is the approximate sampling rate
It's a continuous-time analog low frequency feedback loop. See page 10 and Figure 23 of the RevC data sheet for an explanation:
The low pass corner in the feedback loop is also the high pass corner of the log amp, assuming that it and not the input coupling capacitor dominates the frequency response. If you think of the log amp as a difference amplifier, the integrated feedback (DC) tries to force the input DC difference to zero, which cancels out the effects of the dc offset.
Edited: typo corrected and last two sentences added 1/13/2011
Message was edited by: BobC
Thanks for the additional details.
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