How to analyze complex electronic circuit ?

Thread Starter

Heroz

Joined May 29, 2022
31
In my textbook when analyze circuit I can did because there is only one circuit .
But in practice circuit they contain more than one circuit in large circuit for example :
WradV.jpg
How can I analyze large circuit ?
I found that I need to break circuit into subcircuit ,
But I don't understand when I break it in subcircuit what next should I do ?
Thank you .
 

tyro01

Joined May 20, 2021
61
This is my opinion, but I think it is better not to divide large circuits into subcircuits until you are familiar with the analysis tools. The important thing is to use analysis tools that can handle even large circuits. LTSpice can be used to divide the system into subcircuits, but the reliability of the analysis results will be reduced if the software is not well mastered.
 

Thread Starter

Heroz

Joined May 29, 2022
31
This is my opinion, but I think it is better not to divide large circuits into subcircuits until you are familiar with the analysis tools. The important thing is to use analysis tools that can handle even large circuits. LTSpice can be used to divide the system into subcircuits, but the reliability of the analysis results will be reduced if the software is not well mastered.
Thank you . I have one doubt , How does they design this circuit?
 

Thread Starter

Heroz

Joined May 29, 2022
31
The first thing that you should do is to redraw the circuit so that you can recognize the basic building blocks.
View attachment 280054
Thank you . I have a problem to understand this point this sounds stupid : when connected subcircuit (for example amplifier ) to other subcircuit , I used to think that amplifier circuit will change behavior such as change from amplifier to other function because there are other circuit connected therefore I think it also change behavior but now It's not something like that , each subcircuit are still the same as when they connect alone right?
 

Ian0

Joined Aug 7, 2020
6,661
Have you seen a circuit before that has an op-amp with a transistor in its feedback loop?
What did it do?
 

Thread Starter

Heroz

Joined May 29, 2022
31
This is my opinion, but I think it is better not to divide large circuits into subcircuits until you are familiar with the analysis tools. The important thing is to use analysis tools that can handle even large circuits. LTSpice can be used to divide the system into subcircuits, but the reliability of the analysis results will be reduced if the software is not well mastered.
Is there analysis tool that can handle large circuits.
 

MisterBill2

Joined Jan 23, 2018
13,689
The circuit shown in post #1 actually consists of several blocks, each having two inputs and one output. and some blocks with only one input. Each of those blocks can be defined by a transfer function relating the output to the inputs, and then those functions can be assembled into an overall function.
But, in addition, there is a fair amount of re-organization that can be applied to make the total function much easier to understand. The circuit as shown does not convey any message about signal flow at all, In fact, the appearance is that the intent was very much to hide the actual function of the system.
So the first step in an analysis of that particular circuit will be a redrawing to make the functionality clearer.
 

MisterBill2

Joined Jan 23, 2018
13,689
Certainly the circuit CAN be simulated, no question there. BUT parts never fail due to overloads when using simple simulators. So additional evaluation will be required after the simulator works.
 

Thread Starter

Heroz

Joined May 29, 2022
31
The circuit shown in post #1 actually consists of several blocks, each having two inputs and one output. and some blocks with only one input. Each of those blocks can be defined by a transfer function relating the output to the inputs, and then those functions can be assembled into an overall function.
But, in addition, there is a fair amount of re-organization that can be applied to make the total function much easier to understand. The circuit as shown does not convey any message about signal flow at all, In fact, the appearance is that the intent was very much to hide the actual function of the system.
So the first step in an analysis of that particular circuit will be a redrawing to make the functionality clearer.
Thank you . Sorry I have a question in many textbook electronic circuit analysis there are only one sub-circuit analysis but there aren't any large circuit ( sub-circuit connect sub-circuit) why ? Or maybe it's because they analyze each circuit and combine one right?
 

MisterBill2

Joined Jan 23, 2018
13,689
Thank you . Sorry I have a question in many textbook electronic circuit analysis there are only one sub-circuit analysis but there aren't any large circuit ( sub-circuit connect sub-circuit) why ? Or maybe it's because they analyze each circuit and combine one right?
I mentioned that in post #10, and you are correct. But the analysis of circuits that have feedback becomes quite a bit more complex, as you can imagine. That is, the summation of all of the small block functions becomes much more complex.

The circuit shown in post #1 does have some apparent feedback, but because of the way it is drawn that is not so very clear.
My guess s that it was drawn by a CAD system operator with no electronic knowledge at all.
 

WBahn

Joined Mar 31, 2012
27,854
Thank you . Sorry I have a question in many textbook electronic circuit analysis there are only one sub-circuit analysis but there aren't any large circuit ( sub-circuit connect sub-circuit) why ? Or maybe it's because they analyze each circuit and combine one right?
The notion that textbooks don't provide any coverage of circuits at this level of complexity is a false one -- most certainly do. But it is limited because the focus is on teaching the fundamentals. Also, like most engineering disciplines, there is emphasis placed on problem decomposition -- breaking a problem down into small pieces and then designing a much smaller solution to each small piece, as well as a well-defined interface between it and other pieces.
 

MisterBill2

Joined Jan 23, 2018
13,689
Decomposition is a very powerful method that often works very well. But as I described earlier it is not always simple and easy. Understanding what a circuit is supposed to do is very helpful.
 
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