Determine the response of the circuit H(s)

[AAA2010]

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i divided the circuit into two halves. i did the first half which is from X(t) till A. i got [(1+Rb/Ra)*1/(R1C1)]/[S+1/(R1C1)] but I'm not sure if i did it right and i don't know how to do the second part. can anyone help me please

 

[CEL]

A is simply an amplifier. The voltage at the right side is the voltage at the left side multiplied by the gain A.
The transfer function of the circuit to the right is calculated in the same way you did for the left circuit..
The role of the amplifier A is to separate the two parts of the circuit, so that the input impedance of the second circuit does not influence the first one.