QThe question is, there is a equation in p10 in datasheet. So what is the
meaning about "(5.6)" in the equation, there is also a table lists some
examples .But when I calculate the Av by using above equation, I can not get
the same value as table1.
AThe values (5.6, 9.2, 4.6, 19.5, and 39) are simplified constants. This
equations is a first order (simplified) equation to give the gain. Those
constants represent various variable (gain, resistances) that are grouped
together to have a simple formula. On its own, 5.6 is of little importance.
The Av comes out in unitless gain and needs to be converted to dB to match the
table (20*log Av). Again, the equation offered is only of first order. Some
tuning would be required. I believe the resistor values in the table were
tweaked to get close to called out gain level.