I am given an opamp circuit (noninverting opamp with 1st order lowpassfilter).(adsbygoogle = window.adsbygoogle || []).push({});

Please view the attachment for the circuit.

I have to show that the transfer function H(f)=Uo/Us is of the form:

H(f)=α( 1 + j(f/f1)) / ( 1 + j(f/f2))

Using basic circuit analysis I came to the following (already checked that its correct) transfer function:

H(f)=Uo/Us= (R4/(R3+R4) ) x (R1 + Z2)/R1

Where Z2 is the equivalent impedance of the capacitor C2 in parallel with the resistor R2.

So: Z2 = R2/(jωCR2+1)

After substituting this into my transfer-function equation i cant get it into form they want me to. Again:

How can I get H(f)=Uo/Us= (R4/(R3+R4) ) x (R1 + Z2)/R1 with Z2 = R2/(jωCR2+1) in the following form:

H(f)=α( 1 + j(f/f1)) / ( 1 + j(f/f2))

I tried many times. I am pretty good at algebra but i just cant seem to grasp this one. Could someone please help me out? This is very important to me. If someone feels like something isnt clear then please write it,ill do anything to make it more clear.

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# Homework Help: Transfer-function form of OPAMP-circuit

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