### Q

The question is, there is a equation in p10 in datasheet. So what is themeaning 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.

### A

The values (5.6, 9.2, 4.6, 19.5, and 39) are simplified constants. Thisequations 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.