Transfer Function Ideas

[opacheco]

Hi to everyone,

I am trying to anlyze a classic and vintage audio active equalizer using vacumm tubes inder, this units use severals filters with feedbacks loops in order to get a specific frequency response proposed for the manufacturer. My idea is to get the transfer function vo/vi of the all filters in order to modify to my needed and see the importance and performace of each circuits elements. I have done some work already using the classical network equations (Kirchoff and Network Theorems...) but the works is very hard to do solving systems of equations and mathematics simpllifications and many hours of hand and pen work with a lot of concentration. I would like to get some advises in order to know if does exist any theorical method more easier for get the transfer functions in these kind of electrical/electronical networks using various feedbacks loops in the same net??

I have attached one active filter drawing of the severals in cascaded found in the unit.

I appreciate any advise or help
Thanks anticipated
opacheco.

 

[rjenkinsgb]

That looks a lot like a second order low-pass Butterworth filter?

eg. This is a common opamp implementation:

Some info on the design of these:

https://www.electronics-tutorials.ws/filter/filter_8.html

 

[Tony Stewart]

Except the Ron must be biased to be much lower than the R's and the max gain will be < 1 as a source follower depending on Ron/(Ron+R/2) (?). So the poles may not be equal.

 

[danadak]

Signal Flow Graph to get at T(s).

https://feng.stafpu.bu.edu.eg/Electrical%20Engineering/3127/crs-13461/Files/Lecture%20(5)_4-11-2015.pdf

https://github.com/hanspi42/signalflowgrapher/releases Utilities

Or attached.


Regards, Dana.

 

[The Electrician]

Hi to everyone,

I am trying to anlyze a classic and vintage audio active equalizer using vacumm tubes inder, this units use severals filters with feedbacks loops in order to get a specific frequency response proposed for the manufacturer. My idea is to get the transfer function vo/vi of the all filters in order to modify to my needed and see the importance and performace of each circuits elements. I have done some work already using the classical network equations (Kirchoff and Network Theorems...) but the works is very hard to do solving systems of equations and mathematics simpllifications and many hours of hand and pen work with a lot of concentration. I would like to get some advises in order to know if does exist any theorical method more easier for get the transfer functions in these kind of electrical/electronical networks using various feedbacks loops in the same net??

I have attached one active filter drawing of the severals in cascaded found in the unit.

I appreciate any advise or help
Thanks anticipated
opacheco.

The source shown in your image shows what is apparently a VCVS (voltage controlled voltage source). This is not typically how a vacuum tube is modeled. One resistor is labeled "Rd", typically how a "drain resistor" would be labeled. Also, there is a voltage labeled "Vs" which is what a person would label a voltage in the source of a FET, not the voltage at the cathode of a vacuum tube. Is your active device a vacuum tube or a FET?

Could you please clarify these issues.