Q.
What is the low frequency operating limit for the AD8370 digitally controlled variable gain amplifier
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A.
As long as the input common mode level is set correctly, there is no low frequency limit and operation all the way down to dc is possible. A dual dual supply of +/-2.5 V can be used along with input and output common mode levels of 0V (see Figure 51 on page 18 of the Rev. A data sheet).
To address situations where dual supplies are not convenient, a second option is possible. The AD8138 differential amplifier is used to translate the common-mode level of the driving source to midsupply, which allows dc accurate performance with a ground-referenced source without the need for dual supplies. This application is described in more detail on pages 18 and 19 of the Rev A data sheet.
