# Gas station without pumps

## 2021 September 16

### Last to-do note in book done

Filed under: Circuits course — gasstationwithoutpumps @ 10:46
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I’ve finally removed the last to-do note from the text book. This one was an explanation of the threshold voltage for FETs as the transition between the subthreshold conduction, where the on-resistance has exponential behavior with $V_{gs}$ and the on-region, where it is roughly constant.

I don’t like copying graphs from datasheets for the textbook, so I needed to measure the values myself to make a plot. My first attempt, using the PMV20XNE nFETs that we used for the past few years in class, was a failure.  The typical on-resistance is only 23mΩ, which is too small for the crude measuring setups and low currents that I could get with the Analog Discovery 2.  I ended up mainly measuring the resistance of the test setup, with errors larger than the value I was trying to measure, so I couldn’t even subtract off the short-circuit measurement.

I tried again with a low-power nFET (a 2N7000), using a constant load resistor of 150Ω (so the maximum power dissipation in the ¼-W resistor would be $(5V)^2/150\Omega = 167mW$).

I controlled with the gate voltage with waveform generator, and measured both the drain-source voltage and the drain current. I used the oscilloscope tool and averaged both within a sweep and across many sweeps to reduce noise.

Because the Analog Discovery 2 has only 2 measurement channels, I had to manually copy the measurements into a file for gnuplot, as there was no way to record the waveform generator output with the measurements in a single file (well, there might be with the scripting capabilities of Waveforms 3, but I’ve not explored them much).

I noticed some pretty large offsets when measuring small voltages, so I did open-circuit and short-circuit measurements and used them to subtract off offsets (with the understanding that the current for the open circuit would be about 150µA, because of the 1MΩ impedance of the Channel 1 measuring the open-circuit voltage).

The corrections make a big difference at the low end, where on-resistance is comparable to the resistance of the measurement instrument and test currents are tiny. The correction at the high end is smaller, but still noticeable. The transition from the exponential behavior of subthreshold conduction to the on-region is pretty clear. (Click to enlarge)

Now all I have to do for the next release of the book is do the standard final checks (page breaks, spell checks, and URL checks).  This will probably take me another week.

## 2020 September 11

### Edition 1.1 released today!

Filed under: Circuits course — gasstationwithoutpumps @ 11:49
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I finally released the new version of the textbook today!  (https://leanpub.com/applied_analog_electronics). The book is only slightly longer than the previous edition:

659 pages
337 figures
14 tables
515 index entries
162 references

The chapter on design report guidelines is available free as a separate publication:
https://leanpub.com/design_report_guidelines

At the same time as I released the new edition, I eliminated my COVID-19 sale, so the minimum price is now \$7.99. I will still provide coupons for free copies to instructors who are considering using the textbook for a course.

I may have to do another version before January, as I have not checked the labs for BME 51A yet to see what modifications are needed for doing the labs at home. For example, I haven’t decided whether it is worth buying more blood-pressure cuffs and extra tubing, to have enough to ship one to everyone. I’ll probably have to give up on the drill-press instruction. I’d rather not skip the micrometer instruction, but that would mean buying a lot more micrometers, as we generally share 5 for the whole class.

One nice thing about selling through Leanpub is that purchasers get all future editions published through Leanpub as part of the price—the company is trying to encourage authors to publish book drafts through them, rather than waiting until the book is completely polished. That means that students who got earlier versions of the book will get this release for free, and anyone who buys now will get the benefit of future releases.

## 2020 September 2

### Last to-do note in book cleared

Filed under: Circuits course — gasstationwithoutpumps @ 17:01
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I finally cleared the last of the to-do notes from the draft of Applied Analog Electronics, only a couple of days behind my self-imposed deadline.  I still have to spell-check the whole book again, check for any missing cross-references, and check for overfull boxes.

I’m not going to check that the 211 URLs are all still ok (each one was ok at the time I added it).  I’ll have to rely on readers pointing out newly broken ones to me.  I wasted a couple of hours looking for tools that would to the job for me automatically, but all the ones I tried failed in various ways (outdated Python code that wouldn’t compile, misparsing URLs that worked just fine from clicking on the links on the pdf file, …).  If anyone knows of a cheap (preferably free) URL checker for PDF files that actually works, please let me know!

I expect to release a new version of the book within a week, at which time I’ll probably end my Covid-19 sale price.  People who buy before the new version comes out can get the current price and still get the new version when it is released.  One nice thing about selling through Leanpub is that purchasers get all future editions published through Leanpub as part of the price—the company is trying to encourage authors to publish book drafts through them, rather than waiting until the book is completely polished.

## 2020 March 27

### Lowering price of textbook

Filed under: Circuits course — gasstationwithoutpumps @ 21:21
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To make it easier for people to learn electronics at home, I’m lowering the minimum price of my book to \$6 during the COVID-19 crisis.  I wish I had a ready-to-go bundle of parts and online videos to help people learn at home, but creating such videos would take me a year (though I am seriously considering starting creating such videos during my sabbatical).

Creating a bundle of tools and parts would require working with one of the companies that sells parts (Jameco, Mouser, Sparkfun, …).  The markup they would require to make it profitable for them to do the bundling is pretty high, though, so for now it is cheapest for people to order parts from distributors and tools and boards from China.

## 2019 December 8

### Book Done!

Filed under: Circuits course — gasstationwithoutpumps @ 22:06
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I’ve posted the latest version of the book—the first version I think of as really completed, so I’m calling it Edition 1.0.

The book is available at https://leanpub.com/applied_analog_electronics/ now, but I won’t raise the price until Tuesday, as I announced last week.  I’ve already sent the students registered for the course coupons for a free book, and they have started picking it up.

The new book takes up 28.7MB and has

651 pages
335 figures
13 tables
509 index entries
155 references

The chapter on Design Report Guidelines is available free at https://leanpub.com/design_report_guidelines. If your students need some advice on writing from an engineering professor, this document may be of more use to them than many longer texts.

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