Lessons in Electric Circuits | Hacker News Reader

Lessons in Electric Circuits

allaboutcircuits.com

315 pointslobo_tuerto30 comments

The CircuitLab founder https://news.ycombinator.com/user?id=compumike has written an excellent book

That’s me! Definitely a slow work in progress… Thank you for the kind words of encouragement :)

Unless you’re doing specialized physics, in the electronics world we always talk in terms of current flow – never electron flow.

Rather weird line from the site. My entire training and career have dealt with things from an electron flow perspective and it made understanding nearly every electronics concept easier. If you base your concept of electricity on positive current flow (remembering the words positive and negative are just labels), it makes understanding things like cathode ray tubes much more difficult.

IMO, the ideal is to:

1. Discuss the simplified EE model. The diode with 0.7 forward voltage is the best example, its highly unrealistic, but its also highly useful. ("Reality" is closer to an exponential function, at least at that region of voltage vs current)

2. Discuss that most EE models are unrealistic, but useful. (Vce saturation, MOSFET voltage-controlled transconductor, etc. etc.). EE is filled with _completely_ wrong, but highly useful models. My favorite has to be the "virtual short circuit" model of OpAmps / negative feedback. (OpAmp analysis technique where you simply set the + and - leads of the OpAmp to the same voltage)

3. Have a brief (but not overwhelming), discussion of Maxwell's Equations, which is a more accurate model, but useless in most of EE. Discuss radios and transmission lines (two situations where we have to start leaning into Maxwell's Equations for understanding), but also discuss their simplified models. (Ex: Impedance matched antenna is "just a resistor").

4. Return to the mantra of EE. The entire point of EE is to simplify circuits and simplify models. Its fine to be wrong, as long as the circuit works at the end of the day. It is highly useful to think in the wrong manner on a wide variety of subjects. (Diodes, BJT transistor voltage drops, Simplified OpAmps / negative feedback models). And only use complicated analysis on the cases that you recognize as "worthy" of deeper analysis. (Antennas, Transmission Line Theory, etc. etc.)

5. And now, teach the https://en.wikipedia.org/wiki/Lumped-element_model

What country did you train in? In my EE education, everything was about current, not electrons. EEs don't normally care about electrons, they care about the flow of charge.

I graduated with an Electrical Engineering degree 46 years ago and "conventional current flow" was ubiquitous except on specifically discussing physical elements like CRTs or doped semiconductors - which was only a fraction of what we covered.

You have to pick one, but then you have to ensure that all the materials you're working with agree, just like imperial vs metric measurements.

But I'm not convinced that it helps, outside of semiconductors and tubes, because it can lead to a whole category of misconceptions. I see it come up reasonably frequently:

https://electronics.stackexchange.com/questions/245610/is-vo...

https://electronics.stackexchange.com/questions/139327/elect...

https://electronics.stackexchange.com/questions/490021/how-i...

https://electronics.stackexchange.com/questions/288248/if-el...

If you're taking a top-down or phenomenological approach, best to just start from observing that there is a property called "current" which has magnetic and thermal observable effects and quantifying from there.

That's weird. Every ECE course I took talked about current flow. We only ever touched on electrons when the physical process of doping a semiconductor was discussed. Cathode ray tubes were covered in physics class.

But yeah, when you're manipulating a beam of electrons, keeping track of how many electrons on which plate makes a lot of sense, but that seems to be limit case where the "current of holes" model breaks down.

I have heard that when transistors were new, there were a bunch of people claiming the theory behind them was nonsense because it treated current in p-doped semiconductors as a flow of positive charges (holes.) (These were not physicists - mostly hobbyists, some electricians and maybe a few EEs.)

Once you get to capacitors, inductors, transmission lines and antennas, you are no longer just considering electrons, but also fields (usually via classical approximations to the underlying QED.) In electrolytes, you have both positive and negative ions...

Did you study electronics engineering or electrical engineering? In my experience the former (dealing with semiconductors and integrated circuits etc.) uses electron flow but the latter (designing power transmission and induction motors and transformers etc.) almost universally uses conventional current (then again they mostly deal with AC anyway so maybe it's less important.)

Yes, the operation of cathode ray tubes is an area of physics where the analogy breaks and talking about particles is useful. Which is exactly what parent post said.

Literally all of regular circuit analysis does not obey this convention. I think maybe this post is pedantic more than is useful.

I've done college, undergrad, and post-grad to PhD in EEE and they always define current as positive charge flow rather then electron flow.

Many thanks for the Lessons!

I’m a lapsed EE (gone into SWE), and I really appreciate the clear, from first principles exposition and build up.

Keep up the good work!

This guide has been around since the early 00's. I read it, start to finish (well, some chapters weren't finished back then :) when I was a teenager and it got me started with electronic circuits.

I ended up becoming an electrical engineer and credit this site significantly for giving me the courage to choose EE in uni.

The guide does an excellent job of building up knowledge without assuming any prior knowledge - just what a curious 15 years needed to get started.

dspguide.com is another great resource and thought me Fourier transform when I barely knew what cos() and sin() were.

I wish I had these resources when I was in school. I was studying EE back in the late '80s. I had a textbook with maybe two worked out examples for each concept. The answers to the odd-numbered homework problems were in the back, but just as a number. So if I worked out a long problem and got, say, 5 as an answer, and the answer in the back was, say, -5, I had no real way of knowing if I made a mistake somewhere, or if the answer in the back of the book was incorrect. Working in groups was discouraged as a kind of cheating because you were supposed to do your own work. The professors weren't that interested in teaching because they felt they were there more to rank us. And the teaching assistants were mostly foreign-born with limited spoken English skills.

There is also a complete Romanian version which I've translated more than ten years ago:

https://mihaiolteanu.me/circuiteelectrice/

These lessons were so helpful for my University classes that I wanted to help "spread the word" and show my support in whatever way I could.

Amazing. You even redrew the figures with translated labels. Also, your website design is objectively better than the original.

I've always struggled with electronics texts.

Mostly because, rightly I'm sure, they discuss the individual components, or subsystems common to electronics: what's a capacitor, what's a resistor, what's an oscillator, what's an amplifier.

But where they break down, for me, is they don't put it all together. It's like having your introduction to computers being nothing more than a book on data structures and algorithms.

All important, fundamental concepts, but how do you get from an algorithm and data structure book to writing your own Rogue game, which uses all of those things.

I've never found a book or other treatise that puts it all together, at least for me. Mind, I've never had any formal training. I took an electronics class in 9th grade which basically studied Ohms law and other fundamentals, and at the end I assembled an AM radio transmitter, but I had no idea how that transmitter worked, what choices were made and why, etc. It was just a kit, and more a testament of soldering and assembly skills than anything else. Same with all of those old Radio Shack kits that they used to sell.

I need a "design your own radio" course or something that works from the top down "here's a radio, here's the structure, here's how we work on each part of that, stitch them together, why use this transistor vs that one".

> "design your own radio"

Even before you said this, I was going to recommend the Radio Amateur's Handbook. https://www.amazon.com/arrl-handbook/s?k=arrl+handbook

Get an old one and save money. I haven't looked at it in probably 20 years and it was an amazing reference even back then. The theory of electronics doesn't change and this book does a great job of taking you from basic theory to designing complex circuits.

There's also Horowitz & Hill's The Art of Electronics which some swear by. I probably read the ARRL handbook cover to cover in high school, so I'm biased :-)

I hear you. I took many electronics classes over the years and never seemed to be able to build much intuition. I've often joked that 80% of my engineering training came from YouTube, and it seems to line up.

I found Ben Eater's 8-bit breadboard computer project[1]incredibly helpful in grokking both low-level computers and the electronic theory. https://eater.net/

I also highly recommend the channels bigclive [2], ave [3], eebvlog [4], Louis Rossman [5], and electroboom [6].

For podcasts, I've found The Amp Hour [7] and Embedded.fm [8] to be invaluable. There's also Contextual Electronics [9] if you want a more Udemy-style experience.

As a fun toy, I recently picked up Spintronics [10], which provides an excellent way to grok oscillators and transistors mechanically. If you're just looking to build intuition, this is a great place to start.

The best training I got, though, was sitting next to an EE as he troubleshot his own designs. Anything you can do to get in a room with electronics guys- meetups, conferences, HAM events, etc. is absolute gold.

Best of luck in your adventures pushing electrons around!

[1] https://eater.net

[2] https://www.youtube.com/@bigclivedotcom

[3] https://www.youtube.com/@arduinoversusevil2025

[4] https://www.eevblog.com/

[5] https://www.youtube.com/user/rossmanngroup

[6] https://www.youtube.com/electroboom

[7] https://theamphour.com/

[8] https://embedded.fm/

[9] https://contextualelectronics.com/

[10] https://upperstory.com/spintronics/

> All important, fundamental concepts, but how do you get from an algorithm and data structure book to writing your own Rogue game, which uses all of those things.

Yeah. In practice, a lot of (programming or electronics) education skips the intermediate step and assumes a certain amount of imagination in pattern-matching a solution out of the available pieces.

There's a certain amount of design information scattered about in "Application notes", which are produced by IC manufacturers who want you to use a particular IC and therefore suggest a bunch of stuff you might want to do with it. The largest of these, which is basically a full course on op-amps, and has a slightly legendary status, is Linear Technology Application Note 47. https://www.analog.com/media/en/technical-documentation/appl...

This is where system modeling, differential equations, networks and control theory all come together to make sense of the “how and why” in using circuit components. That is years 2 and 3 in the EE curriculum—-at least it used to be.

This got me through my electrical engineering degree and studying for EE interviews. Still use it whenever I need to brush up on op-amp math

Lessons in Electric Circuits - https://news.ycombinator.com/item?id=9379307 - April 2015 (11 comments)

For physical books, I picked up these at a used book store and found them wonderful: Basic Electronics (Valkenburg, 1954). Something about those vintage illustrations.

Kind of nice they don't put up a window asking you to subscribe ... books that is. :-)

https://archive.org/details/basic-electronics-volumes-1-5-by...

Coverage-wise, this is pretty close to the EE textbooks used in my sophmore and junior years. Depth-wise, it emphisizes the practical aspects of circuits whereas the textbooks in college had both practical as well as theoretical material. With some concetrated study and maybe some additional texts for reference, you should be able to have a really good, broad understanding of circuits.

If you are interested in learning electrical principals and want a practical application but don't know where to start, look into getting your ham radio license (three license tiers, each with more electrical knowledge required).

I recently passed my extra-class exam and had a lot of fun learning in the process.

Where/how did you learn the electrical principles?

See my post: https://news.ycombinator.com/item?id=34340611

Have been looking for something of this nature for months - thanks!

Reply on news.ycombinator.com