Analyze this opamp active filter circuit

AI Thread Summary
The discussion focuses on analyzing an op-amp active filter circuit to determine the function Vs/Ve. The original poster struggles with simplifying the circuit and expresses uncertainty about their equations. Participants suggest using Kirchhoff Current Law (KCL) to derive simultaneous equations for the circuit's gain and recommend solving it using both KCL and phasors. There is a correction regarding a sign convention error in one of the equations presented. The conversation emphasizes the importance of verifying results through multiple methods.
ace130
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Hello, so this the circuit of an IdeaI OPAMP.
R7Umlxl.jpg

The Question is to find the function Vs/Ve .
I tried to make some sum ups to simplify it but I still unable to find a solution, so I tried to NOT sum up any component and found this:
E-S=iZ+i2(Z+R)
E=iZ+i3R
S=i2R

so the idea is to find E=f(i2) , This is the final Result but I'm not sure if it's correct :
50QjLNT.jpg
 

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ace130 said:
Hello, so this the circuit of an IdeaI OPAMP.
View attachment 219618
The Question is to find the function Vs/Ve .
I tried to make some sum ups to simplify it but I still unable to find a solution, so I tried to NOT sum up any component and found this:
E-S=iZ+i2(Z+R)
E=iZ+i3R
S=i2R

so the idea is to find E=f(i2) , This is the final Result but I'm not sure if it's correct :
View attachment 219619
I'm not quite sure what you are doing with your equations, but are you familiar with how to solve circuit problems using the Kirchhoff Current Law (KCL) equations? I would write the KCL equations for the two nodes in the middle (the - input of the opamp and the middle connection point between the 3 capacitors), and solve those simultaneous equations for the gain of the circuit s(t)/e(t).

Also, are you supposed to be solving this with phasors or differential equations?
 
Yes i know the KCL , also this should be solved in complex .
I don't know if I should sum up those Rs and Cs or just write KCL that will take more time
 
ace130 said:
Yes i know the KCL , also this should be solved in complex .
I don't know if I should sum up those Rs and Cs or just write KCL that will take more time
I don't know of a technique to "sum up" the Rs and Cs, but there may be one. Why not do it both ways to check your answer?

Can you show us the two KCL equations that I mentioned? Then show how you would solve them simultaneously...
 
this is the KCL and loops
frLP0ia.jpg


and this is the final result:
50Ri9vs.jpg

Edit : the final line it should be Zc not 1/Zc .
 

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Your equation (2) is not right. It suffers from a sign convention error.
 
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