[sdiy] Becoming better at understanding difficult analog schematics

[Paulo Constantino]

The most frustrating part for me is that I understand all the basic
building blocks in electronics: all types of transistor amplifiers, op-amp
amplifiers, oscillators, many types of filters, current mirrors,
differential amps and so on, but still, many schematics I look at look
nothing like those. They have transistors, capacitors and resistor
feedbacks all over the place that I cannot assign as any types of
amplifiers, or other building blocks that I know of. It's like the designer
just thought of a circuit in steps, realizing what the voltages and
currents are doing at a certain point and then adding feedback and extra
paths to those points in steps, but then the end product is not easily
understandable.
I'm not sure how to describe this. It looks kinda like someone building a
structure using lego blocks, adding bridges from place to place.

On Sun, May 12, 2024 at 6:40 AM brianw <brianw at audiobanshee.com> wrote:

> I studied Electrical Engineering, but I do not recall any course that
> actually taught how to read schematics, per se. However, there are some
> basics like Kirchhoff's Laws (current and voltage) which typically test
> your ability to unwind a schematic, and I think that understanding those
> laws helps decipher a schematic.
>
> There's also a general style for schematic flow that almost everyone
> follows. There are, of course, many slight variations on that general
> style, but most variations are not too upsetting.
>
> I did once work on a prototype designed by a very famous early electronics
> era person, and the style was so out of the ordinary that I could not make
> sense of it. In a way, this exception almost proved the rule that most
> designers try to arrange things the same way everyone else does, to improve
> understandability.
>
> By the way, I spent some time reverse-engineering guitar pedals from the
> circuit board traces. That was an interesting exercise, because the
> arrangement of parts and traces on a board is not the same as it is in the
> 'standard' schematic flow. I would write down the schematic as it was
> arranged on the board, as a first draft, and then rearrange the 'same'
> schematic in the 'standard' flow. The second draft would also group things
> into high level blocks, to make them more readable. Guitar pedals are so
> small that the physical components cannot be separated into high level
> functions - instead they might be tightly interwoven. That might be another
> exercise that could help you rearrange components in your head while
> reading schematics.
>
> Finally, learning the basics of op-amp theory (no current in or out of the
> inputs, at least not in the steady state, etc) might help you understand
> feedback a little better. Of course, not all circuits with feedback use
> op-amps, and discrete transistors usually require more than basic
> electronics to understand, but a little knowledge might go a long way.
>
> Brian
>
>
> On May 11, 2024, at 4:41 PM, Paulo Constantino wrote:
> > Hi all,
> >
> > I wanted to ask a question that has been on my mind lately.
> >
> > I consider myself a beginner in electronics.
> > I know all the fundamental stuff, or how can I express it... I
> understand the landscape of electronics from a high point of view.
> >
> > However what gets me constantly is this...
> > When I look at analog electronics schematics, specially big ones, they
> don't make sense to me, or at least not within the first few minutes of
> looking at them. I find that most schematics are highly "non-linear". By
> that I mean that there are feedback loops everywhere, many times from
> places in the schematics that are far away from each other.
> >
> > Schematics that are more linear flowing are easier for me because I can
> see the "blocks" and how they connect to each other. But many schematics
> are so non-linear and I find that difficult to understand.
> >
> > How to become better at this? If you are an experienced electronics
> engineer, can you yourself understand these "non-linear" schematics by just
> looking at them if you have not seen that type of circuit before?
> >
> > Thank you very much for reading this and responding if you can.
> >
> > Paulo
>
>
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