Hello everyone! I'm new to AD620, I've already read the datasheet of AD620,but still i have some confusion of how does AD620 work. The picture above is the Simplified Schematic of AD620.I1,I2 are the constant-current source.When +in has a positive signal the base current of Q2 will go up and so the collective current of Q2 will go up accordingly. But I2 is the constant-current source ,so where the extra collective current comes from? By the way,what 's the function of C1 and C2? Wish someone help me, thanks!