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. https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1 -- Thanks, - Win
AoE x-Chapters, 4x.26, MOSFET current source, nodal analysis
Started by ●August 9, 2019
Reply by ●August 9, 20192019-08-09
On Friday, 9 August 2019 21:50:34 UTC+1, Winfield Hill wrote:> 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. > > https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1loopy noodle analysis? :) Brain will have to wait to take it in.
Reply by ●August 9, 20192019-08-09
On 9 Aug 2019 13:50:20 -0700, Winfield Hill <winfieldhill@yahoo.com> wrote:> > 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. > >https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1I 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.
Reply by ●August 9, 20192019-08-09
John Larkin wrote...> > On 9 Aug 2019, Winfield Hill wrote: >> >> 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. >> >>https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1 > > I Spice stuff like that. That includes nonlinearities, > real part models, and lets me quantify things like > step response accuracy."Some designers turn to SPICE to analyze the circuit, but be aware that the MOSFET�s SPICE model will likely be highly defective at low currents, see Figure 3x.35, not to mention possible problems with the op‐amp�s capacitive‐load model at high frequencies" The Figure 3x.35 reference is in Chapter 3x.5, posted: https://www.dropbox.com/s/0ph15moamo0mlt4/3x.5_MOSFETs_Linear-Transistors_DRAFT.pdf?dl=1 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
Reply by ●August 10, 20192019-08-10
On 9 Aug 2019 17:55:28 -0700, Winfield Hill <winfieldhill@yahoo.com> wrote:>John Larkin wrote... >> >> On 9 Aug 2019, Winfield Hill wrote: >>> >>> 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. >>> >>>https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1 >> >> I Spice stuff like that. That includes nonlinearities, >> real part models, and lets me quantify things like >> step response accuracy. > > "Some designers turn to SPICE to analyze the circuit, > but be aware that the MOSFET�s SPICE model will likely > be highly defective at low currents, see Figure 3x.35, > not to mention possible problems with the op‐amp�s > capacitive‐load model at high frequencies" > > The Figure 3x.35 reference is in Chapter 3x.5, posted: >https://www.dropbox.com/s/0ph15moamo0mlt4/3x.5_MOSFETs_Linear-Transistors_DRAFT.pdf?dl=1 > > 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.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
Reply by ●August 10, 20192019-08-10
On a sunny day (9 Aug 2019 13:50:20 -0700) it happened Winfield Hill <winfieldhill@yahoo.com> wrote in <qikmac01pg9@drn.newsguy.com>:> > 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. > >https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1do not use '&' in filenames do not use spaces in filenames># xpdf 4x.26_Loop\ &\ Nodal\ Analysis.pdf[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/
Reply by ●August 10, 20192019-08-10
On a sunny day (Fri, 09 Aug 2019 20:44:29 -0700) it happened John Larkin <jjlarkin@highlandtechnology.com> wrote in <7ceske9roatjlumf42l7lb3lcj4tqgcmum@4ax.com>:>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.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,
Reply by ●August 10, 20192019-08-10
"Jan Panteltje" <pNaOnStPeAlMtje@yahoo.com> wrote in message news:qiljlc$u5k$1@dont-email.me...> do not use '&' in filenames > do not use spaces in filenamesBwahaha, 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/
Reply by ●August 10, 20192019-08-10
On 8/9/19 4:50 PM, Winfield Hill wrote:> 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. > > https://www.dropbox.com/s/7zl3yi789idg3s8/4x.26_Loop%20%26%20Nodal%20Analysis.pdf?dl=1 >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.> We can also write that v3 is higher than Vg by the voltage i3 R3 > across R3.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. ;)> We can also write that v3 is higher than Vg by the voltage i3 R3 > across R3.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. ;) <https://www.youtube.com/watch?v=9wWUc8BZgWE> 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.)> We’ll assume the voltage across R1 is equivalent to our current > output.That assumption needs motivating--it assumes that R3 >> R1, for instance.> If we assume the (alpha+beta)/(alpha‐1) term is about unity, the > equation says the op‐amp’s influence is going away above a cutoff > frequency fc = 1/2pi R2 C2, which is not a surprise.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? >But this is still pretty fast, current pulses 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
Reply by ●August 10, 20192019-08-10
