Electronics > Beginners
How woud an experienced person "know" how to build the circuit?
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Siwastaja:
Often, most of the design time is spent trying to find the combination of components that can do the job - especially if we haven't solved the same problem before and hence don't know where to start designing. This means countless parametric searches on Digikey, skimming through hundreds of datasheets just to find an IC to do (part of) the job. The bigger the part a single IC does, the better - we all dream about easy single-chip solutions. Then, you'll find out that the more integrated ICs, which look perfectly ideal on the first datasheet page, giving you high hopes, do more things wrong, or opposite to your specific requirements. So you are back to using multiple ICs, or typically need a combination of passive components, discrete semiconductors, simple ICs such as opamps or logic gates, and highly integrated ICs. At the same time, you need to make sure the components you choose will be available for production, or that replacements exist. Especially during the current component manufacturing/sourcing crisis, this has gotten more difficult.

While playing this game, the "schematic" changes all the time, based on these limitations on parts you can find. And once you find the right parts, the schematic is mostly fixed, through the combination of application notes describing "typical" usage, added with a bit of your own ingenuity, some "basic" building blocks you have acquired over the years in your mind, and by Googling how others have solved similar problems. And, sometimes it's a lot of tedious brainwork in the front of a simulator and/or soldering iron&scope trying things out, sometimes quite randomly.

Then, we throw in all the "rules of thumb" to save time, add some components randomly without doing due analysis, and sometimes we shoot ourselves in the foot in the process, requiring respin / aftermarket fixes or so.
Beamin:

--- Quote from: tpowell1830 on June 27, 2018, 02:03:49 am ---Hmmm... don't have a reply to your question, but after looking at your previous posts and this one, you ask some very thought provoking, interesting questions.  :)

--- End quote ---


Thank you others here have said the same thing. And even some others get annoyed at these questions because their brains are very linier. When I was in elementary school my gifted and talented class teacher thought us to "Think out side our comfort box". Try solving things that were hard or coming up with solutions where the obvious answer was none, or the status quo answer no one questioned. Doing this in business I was able to add lines of revenue we didn't have before or turn expenses into profits. You know you are doing it right when people say "I would have never thought of that" or "That will never work it has nothing to do with this." I also never use the word "can't", not even in my head, and subconsciously that leaves my mind open to explore solutions.   
Raj:
Curcuit building depends highly on what you've been trying to make ,in my prospective.I ask the following-
Has it already been made?
if yes-Did it have a room for improvement?
         How can I improve it?

If no,what is going to be the purpose of it?
What parts/ already available modules/ parts of other people's circuit can achieve that
what circuit layout is best

then i'll see how i can bring power consumption,cost,interfearance and glitches down.
it'll involve -calibrations.
lots of measurement.
seeing and calculating where can I switch to cheaper and more common components. (this is where the main theory parts comes in).
trying to bring the number of different parts down. etc etc

 then I try to meat compliances


But all of the above is only when I try to make something for others.
If I am making it for myself, Money is non issue and I get batsh!t crazy,making multiple prototype boards.

But let me tell you.There's nothing new under the sun.
Most of the time,what we are doing is making the same things smaller/faster or with alternative parts,specially if the previous thing can't be made anymore because of parts being manufactured no more.
tggzzz:
The answer is simple. You:

* read about standard components and building blocks, and understand how/why they work
* define what you want to achieve, numerically where possible
* read and research how others have done it before
* understand how well/poorly previous solutions match your requirements
* understand how well/poorly previous solutions have worked, and why they work
* think about how to divide your requirements into lots of smaller sub-units
* repeat 3,4,5 for the sub-units units
* work out how you are going to test whether each of the sub-units is functioning as you expect
* calculate the values of the critical components
* choose suitable components
* build
* test each sub-unit
* where something isn't performing as you expect, understand why and calculate replacements
* rinse and repeat 1-13 as appropriate
No, that isn't easy. It requires a lot of work over many years. Gradually you improve.

Note that the key points are research and understanding of the theory. Without those you are a caveman fumbling in the dark.

It also helps to have point 2 sorted out, although it can change over the course of time.
Audioguru:
When I design a circuit I want it to work properly. Then I do not "guess" at parts values, or fiddle with many values until the circuit barely works when I build it wrong. Instead I calculate parts values with datasheet spec's of active parts and choose parts values that will allow the circuit to work properly when the spec's for an active device is minimum and maximum. Then every circuit I build works properly.

I have modified many circuits so that they do what I want and I have modified many circuits that do not work where the parts are wrong because their values were guessed or because the designer never used datasheet specs.

Minimum and maximum specs are important because when you buy a transistor you do not know if its current gain is low or is high, and each one is probably different. I design a transistor circuit so that it works properly with a transistor that has any passing current gain.   
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