Here's a new section I'm hoping to complete, so it can be added to the x-Chapter book before it goes to the printer in a few weeks. Please look it over, but don't be too harsh, about its lack of mathematical vigor. It's closer to our usual back-of-the envelope approach to calculations. Fixes for errors, suggestions for clarification, improved accuracy, and comments welcome.
--
Thanks,
- Win
loopy noodle analysis? :) Brain will have to wait to take it in.
I Spice stuff like that. That includes nonlinearities, real part models, and lets me quantify things like step response accuracy.
Besides, I've forgotten most of that college math.
"Some designers turn to SPICE to analyze the circuit,
be highly defective at low currents, see Figure 3x.35,
capacitive‐load model at high frequencies"
The Figure 3x.35 reference is in Chapter 3x.5, posted:
This is one of those case where relying on SPICE is not a good idea. Plus, when you have an analytical solution to your circuit, you can more easily see what the trade offs are, and optimize the circuit.
--
Thanks,
- Win
But how does the analytical solution deal with nonlinearities, like the low current that you mentioned? A bunch of small-signal math analysies, at different operating points, is not only tedious, they miss the point, that the circuit will be nonlinear during a single event. Like, for a current step, an opamp may wind up in the region where the mosfet is barely turned on, and overshoot later when fet gain is high.
I personally don't "see" much in an analytical solution. Some people do. I do see a lot in a waveform or a stepped-parameter set of waveforms.
Sometimes "good" can't be expressed as an equation. Usually goodness is a complex tradeoff that can't be quantified: tune it until you like it and think you can sell it.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
On a sunny day (9 Aug 2019 13:50:20 -0700) it happened Winfield Hill wrote in :
do not use '&' in filenames do not use spaces in filenames
[2] 11547 zsh: command not found: Nodal Analysis.pdf # Error: Couldn't open file '4x.26_Loop ' [2] + exit 1 xpdf 4x.26_Loop\# mv 4x.26_Loop* 4x.26_loop_and_nodal_analysis.pdf
# xpdf 4x.26_loop_and_nodal_analysis.pdf OK now
# mv 4x.26_loop_and_nodal_analysis.pdf winfield/
On a sunny day (Fri, 09 Aug 2019 20:44:29 -0700) it happened John Larkin wrote in :
Right, the inventor of the wheel did a great job. The fight over Pi came later.
J.P. Weapons of math destruction
In the future it will be all AI neural nets, no questions asked, and no answers given.
You gotto know a little bit about maaz though (if only to pass the exams) but beware of strings theory attached,
Bwahaha, it's 2019. You old *nix fogies are still having problems with this?!
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Nice. I like your making a virtue out of a necessity (hand-drawn figures). ;)
One point that might be worth a footnote is that Kirchhoff's laws are a low-frequency approximation, applicable only when radiation and self-capacitance are negligible. It's surprising how many folks (even some who know more about antennas than I do) treat them as Holy Writ.
Of course, K's laws are at about the same level of approximation that allows us to draw schematics and reason about them, but they aren't on the same level as conservation of charge, for instance.
I know what you mean, but "higher than" might not be the best phrase when i3 R3 can be negative. A friend who's a much better writer than I am uses the acronym RWWATP: Real Writers Write Around The Problem. ;)
This is true of course, but the following equation needs another sentence or two of introduction, or you'll lose people. A sentence like "This ignores the DC output of the amplifier, which is OK because we're doing a small-signal AC analysis here." It's a bit confusing because the middle bit is an approximation but the last bit is exact.
The middle bit also assumes that the frequency is low enough that the inverting and noninverting gains of the amp have the same magnitude, but you don't say that anywhere. Maybe write the equalities in order from exact to approximate?
Your wheeling in your colleague Alan Stern to do the math reminds me a bit of Woody Allen in "Annie Hall", when he pulls Marshall McLuhan into the scene. ;)
In the expression for Zg, you're assuming that the drain is sitting still. You do say you're ignoring Crss, but a sentence explaining why that's OK would be helpful. The Miller effect is usually pretty important in high frequency analyses. You're also ignoring the Early effect, which can be important even in small-signal situations because it limits the available voltage gain. (Is there a better name for the Early-effect equivalent in MOSFETs?)
At the top of P3, Zg = 1/sCiss + R1.
I'd leave out the 'duh's. (I assume you would too, but they might get overlooked in editing. That commonly happens with swear words in source code comments, for instance. Very embarrassing.)
That assumption needs motivating--it assumes that R3 >> R1, for instance.
There's apparently nothing motivating this assumption--it would be clearer stated the other way round. That whole paragraph is too terse, I think. Which terms are being neglected, and what additional assumptions does that involve?
Comma splice alert! ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
That should be writ large, and engraved in all university courses.
Unfortunately it is becoming a lost art :(
OK, thanks, good suggestion for DropBox links.
--
Thanks,
- Win
On a sunny day (Sat, 10 Aug 2019 01:25:33 -0500) it happened "Tim Williams" wrote in :
You silly widows users still do not understand the world is MUCH greater than your latest auto update security hole.
Phil, thanks very much for your comments, I have made a dozen changes. And Paul will no doubt rework it further as well.
--
Thanks,
- Win
Windows? No, I mean I don't even hear my Linux friends complaining of shit that archaic. They used to. I assume it's been fixed. Are you using 90s Redhat or something? Update that security hole!
Or they still mumble about it but have resigned themselves to hopelessness over the years...
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Learning classic circuit theory and analysis is critical to doing original circuit design, but it's just the starting point.
Design is the opposite of analysis. And most all the interesting stuff is seriously nonlinear.
What the theory can do is provide insight, guide creative fiddling. Ultimately most of us solder parts to boards to make stuff that works, not publish papers.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
From wiki:
Brother Cadfael is the main fictional character in a series of historical murder mysteries written between 1977 and 1994 by the linguist-scholar Edith Pargeter ...
That's funny. Her continuous comma splices make the books almost unreadable.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Well, they're still valid locally. You wouldn't use a transmission line (as such) and assume the currents through one wire of it are equal at both ends; but you can assume so for the two terminals of each port. Likewise, the assumption breaks at frequencies where higher order (non-TEM00) modes are active; but at those frequencies, we don't call it a transmission line anymore (well, descriptively perhaps, but not theoretically).
More accurately, the applicable locality is proportional to wavelength times approximation tolerance. In the lambda-->0 limit, it's simply the conservation of charge for a differential volume, or, rewritten a bit... Ampere's or Faraday's laws I think?
This kind of discussion can quickly get pedantic, but it's a good idea to have somewhere. It's beyond the scope of this section; but, the transmission lines section, I believe, has yet to be seen? That's the perfect place. Just dropping a footnote to it here, would be nice. (Also in the section on R/L/Cs and their equivalent circuits, which arise for similar reasons; and probably other places?)
Regarding the formatting here -- it may feel better with omega_1 and omega_2 terms (1/RC), instead of alpha and beta (frequency-dependent gain terms), or maybe included in them, or maybe doing omegas first and then instead of the rational expression with alpha and beta, a shorter H is used? I'd have to play around with the algebra a bit to see what's neater. Anyway, that might arguably be just an editing thing as well?
Another assumption that I didn't see supported: ignoring the current in the sense resistor. We all know what we're doing, at least in the usual (high output current) case, but you're also talking about microcurrent sources, for which the resistors will be similar value, or the shunt resistor might even be larger. In that case we cannot ignore the contribution.
A direct consequence is, instead of treating the opamp as an integrator, it's an integrator+1 term -- the +in signal gets feed-forward into both the gate and the shunt, giving weird DC and non-minimum-phase AC terms/errors.
An inverting configuration would be more honest here, if inconvenient; but, I wonder also if this would have any potential improvements for dynamics? May be worth testing. I suppose a noninverting integrator configuration might also be possible (a variant on the Howland charge pump, with C load, but also with inverting feedback), again with the possibility of different performance.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Completely understood and accepted. Anything significantly non-linear virtually requires number crunching rather than standard analysis.
Nonetheless, an analytical solution to a /simplified/ model can yield valuable insights. The classic simplified model in physics is exemplified by "...assume a spherical cow...".
There are many similar things in electronics, e.g. simple model are used to estimate EMI/EMC between one comms system and another. Imperfect? Of course; it never matches reality. Useful? Yes.
Circuit design starts with the topology problem: what is the schematic that we want to analyze? Where does it come from?
In my EE school, when I talked about designing things I was told "Undergrads don't design; that starts in graduate school" so I didn't apply for grad school.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
On a sunny day (Sat, 10 Aug 2019 08:44:21 -0500) it happened "Tim Williams" wrote in :
What security hole? It '&' is just part of the bash syntax and means run program in the background.
Try reading a book on Unix, almost everything runs on Linux these days except for some silly widows computers in homes of people who have not bought / borrowed / stolen / rented / learned / what else have you a clue.
Why do it to yerselves?
And no this system is lemme see ~ # uname -a Linux panteltje12 2.6.37.6-smp #1 SMP Sat Aug 3 19:23:48 CEST 2013 i686 AMD Sempron(tm) 145 Processor AuthenticAMD GNU/Linux
Slackware, probably the most sane distro there is.
Why bother updating? 'tworks right no?
Sure YOUR system may need updating because yet an other processor security disaster was discovered last week.
I KNOW intel procesors are part of the NSA spy network. That is why I keep the invasion plans carved in stone^H^H^H^H^HMDISC hidden so they do not know the Orange House will be taken at noon.
That is why I run AMD so that sensitive data is not made public.
U Use Intel I Presume?
Huwei is releasing their own replacement for android shortly, thank Agent Orange's tariffs I may just get one, I do not like android, this can only get better, Dunno if it is Linux based...
UUGH
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