Find Transfer Function of Circuit: KVL, KCL Equations Used

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Discussion Overview

The discussion revolves around finding the transfer function Vout(s)/Vi(s) of a given circuit, utilizing KVL and KCL equations. Participants explore the complexities of the circuit, including the roles of various components and the implications of circuit topology on the transfer function. The context includes both theoretical and practical aspects, with references to software tools for circuit analysis.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes the need to include R2 in the transfer function calculation, as it loads the rest of the circuit.
  • Another participant expresses confusion regarding the grounding in the circuit.
  • There is a suggestion to use simulation software like SPICE for circuit analysis, although it does not generate transfer functions directly.
  • Some participants discuss the feasibility of calculating the transfer function by hand, with one suggesting that it may be very difficult due to the circuit's complexity.
  • There are mentions of alternative software tools that can plot frequency responses but do not provide closed-form transfer functions.
  • One participant indicates a desire to compare results from SPICE with MATLAB using transfer functions, indicating a homework context.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of including certain components in the transfer function and the challenges of calculating it by hand. There is no consensus on the best approach to find the transfer function or the most effective software to use.

Contextual Notes

The discussion highlights limitations related to the complexity of the circuit and the assumptions regarding component interactions, such as the coupling coefficient of transformers. There are unresolved questions about grounding and the implications for circuit analysis.

Who May Find This Useful

This discussion may be useful for students and practitioners in electrical engineering or related fields who are working on circuit analysis and transfer function calculations, particularly in a homework context.

ozerozdal
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Homework Statement


Find the transfer function Vout(s)/Vi(s) of the circuit


Homework Equations


Zr = R; Zl=Ls; Zc=1/Cs; KVL; KCL


The Attempt at a Solution


I have to find the transfer function of the complete circuit I send.For this, I divided the all circuit into small pieces.I tried to write the function for the smallest one,and then I realized that all circuit is not a series circuit.By the way, Vac source our input, and output is in front the R2.For this reason,I didnt add R2 into transfer function ? Am I right or should I add it ? Also how can I find the transfer function for the second and the complete circuit ? Can you give me an idea ?
 

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ozerozdal said:

Homework Statement


Find the transfer function Vout(s)/Vi(s) of the circuit


Homework Equations


Zr = R; Zl=Ls; Zc=1/Cs; KVL; KCL


The Attempt at a Solution


I have to find the transfer function of the complete circuit I send.For this, I divided the all circuit into small pieces.I tried to write the function for the smallest one,and then I realized that all circuit is not a series circuit.By the way, Vac source our input, and output is in front the R2.For this reason,I didnt add R2 into transfer function ? Am I right or should I add it ? Also how can I find the transfer function for the second and the complete circuit ? Can you give me an idea ?

Welcome to the PF.

Yikes, that last circuit is involved!

For the first circuit, yes you need to include R2 in the calculation, since it loads the rest of the circuit. Are you told to assume the coupling coefficient of the transformers is 1?
 
Thanks for your reply.Yes I assume the coupling coefficient of the transformers 1:1Actually I am confused for the grounds.How can I think them ?
 
Get simulation software like SPICE - quick! :bugeye:
 
Is there a software which gives us the transfer function of the systems directly? Also,will it be too hard to calculate by hand ?
 
ozerozdal said:
Is there a software which gives us the transfer function of the systems directly? Also,will it be too hard to calculate by hand ?

SPICE does not generate transfer functions. It allows time response to various input functions, and frequency domain information (Bode plots).

You can input transfer functions but you don't get transfer functions generated from circuits input'ed into the software.

i know of no software that does that, but it's conceptually feasible so maybe there is some out there.

Doing a circuit like your #3, or even #2, by hand is next to impossible. Only possibility I see is application of two-terminal network theory (ABCD parameters etc.) but even there the mutual inductances seem to complicate the situation. Also, who knows, maybe constant-k or m-derived theory - I'm not conversant with those.
 
rude man said:
SPICE does not generate transfer functions. It allows time response to various input functions, and frequency domain information (Bode plots).

You can input transfer functions but you don't get transfer functions generated from circuits input'ed into the software.

i know of no software that does that, but it's conceptually feasible so maybe there is some out there.

But you can plot Vo/Vi with SPICE, at least I can with MicroCAP...
 
berkeman said:
But you can plot Vo/Vi with SPICE, at least I can with MicroCAP...

Of couse, but the OP was asked to find the transfer function, which I understood to be in closed form, e.g. Laplace. But maybe Bode plots is what the question had in mind after all.
 
Yeah I can plot signal-frequency, phase-frequency with LT Spice but to compare it,I want to draw the same graphs with MATLAB using transfer function of the circuit.Actually this is my some kind of homework.
 

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