QThe AD8306 datasheet mentions a "special dc-offset sensing cell" (page 7) to
null residual input offset. For our fast optical range finding application I
would be interested in the time constant (response time) of this dc-offset
-sensing that possibly limits our sampling speed.
AThe internal offset compensation loop in the AD8306 has a high-frequency corner
which allows for accurate measurement of input signals down to 5MHz. Above 5MHz
the speed of the compensation loop shouldn't have any impact on the device's
measurement accuracy. If you want more info on how this loop works I suggest
you look at pg.11 in the AD8309 datasheet. Both of these devices are internally
the same, the AD8306 only differs in that it is laser trimmed to have less
variation in slope and intercept.
Some additional log amp information can also be found in the AD8307 datasheet.