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!

Hi Sun,

I am looking into this and will get back to you soon with more detail.

For the function of C1 and C2, these capacitors together with the preamp transconductance actually determine the gain-bandwidth product of the amplifier.

Best regards,

Emman