ryang wrote on Apr 27th, 2009, 4:12am:The datasheet I am referring is actually AD8628 of Analog device.
As we can see from the datasheet, the large signal voltage gain is typically 110dB.
However, as is shown in fig.16, the open loop gain is even less than 70dB.
Former 110dB is open loop gain for very low frequecny or almost DC signal.
ryang wrote on Apr 27th, 2009, 4:12am:By the way, I noticed that the large signal voltage gain is tested with a load resistor, while the open loop gain is tested without any load.
Is it affects the result? Which one exactly should I take?
Both are open loop gain.
But former is DC open loop gain. Here you can ignore frequency characteristics due to load.
On the other hand, data sheet argue frequency characteristics of open loop gain in Fig.15 and Fig.16.
Here you can not ignore frequency characteristics due to load.