I have derived the stage 1 and stage 2 transfer function separately (both have their own feedback and schematics). I tried just to assume that the transfer function of the two stage as multiplication of both TF1*TF2.
My problem I don't know how can I get the full transfer function with the feedback coming from second stage output to first stage input through R1 as I don't know how I calculate the current flowing through R3. Is there a technique I can think of?