Hi all,

I'm in my first semester of EE and for this weeks tute questions I've been asked to calculate the formula for the frequency dependent complex, phasor transfer function for this circuit:

I'm a bit stuck, the question sheet gives the hint of writing KCL equations at the Vx and V- nodes but that hasn't helped me too much yet. This is what I've tried to do:

excuse the crappy drawing..

I'm a bit lost of where to go from there though, was I supposed to have I(out) in the second KCL equation so that I'd be able to solve for Vin/Vout? How would I do this? My knowledge of OP amps is a bit sketchy, it wasn't taught that well.

If I'm totally off (I suspect I might be!!) let me know.

Thanks.

 

Your equation at node Vx is wrong. Using KCL at node Vx:

(Vin-Vx)/10kΩ - Vx(s*0.1uF) - Vx/10kΩ - (Vx-Vout)/10kΩ = 0

That should help you.

BTW, what you have is a multiple feedback lowpass filter.