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Talk:Negative resistance/Archive 7

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Neon lamps as negative resistance devices

Latest comment: 8 years ago13 comments3 people in discussion

Neon lamps and their cousins should not be mentioned as negative resistance devices.

The usual story is somebody collects some data points and draws a static IV curve. The problem is the IV curve is not time invariant. It gets modified by the changing concentration of ions throughout the tube. At low currents, there are few ions and the electric field is uniform; after breakdown there's a huge change: there's a high field at the cathode fall. It takes time for the heavy ions to migrate to the cathode to set up that field. The internal structure of the device is changing.

To put it another way, the neon lamp has internal state.

I don't think of an electromechanical buzzer as a negative resistance oscillator; it depends on a spring and a slowly moving inertial armature; I have the same view of neon lamp relaxation oscillators. In any event, a neon bulb is not a simple negative resistance device; there's a lot going on; the internal state of the device is important.

Also, some IV curves are not carefully drawn. Discontinuous jumps and unstable regions are ignored in order to get a conventional-looking curve. File:GlowDischargeVoltAmpere.jpg has a gap between D and E; the redrawn File:Glow discharge current-voltage curve English.svg omits the gap; File:Glow discharge current-voltage curve vertical.svg is based on same image but has sloping returns and adds hystersis. These graphs become so common place that they are accepted without references.

Compare the figure above to the figure here. They are much different. Which one is right? What's going on?

See also Reich (1944) Theory and Application of Electron Tubes, 2nd ed., McGraw-Hill, pp 417 ff. (compare dynatron, p. 380.)

IIRC, some other references describe a slight negative slope on the vertical portion of the second graph just below B, but that small curvature is not something that the conventional relaxation oscillator exploits.

Another reference maps instabilities in the IV plane for hydrogen discharge tubes. Sadly, I cannot find that ref right now.

Do those instabilites show a negative resistance curve or that the ions distribution cannot find a stable configuration? No matter what, it means the IV characteristic is changing; it's not a static thing; that makes neon lamps a lousy example of a negative resistance device.

There's also that thorny little issue about the neon lamp needing some background radiation to generate the initial ions. There's a lot of additional state for a complete description of the neon bulb.

Even the negative resistance portion of an arc discharge is more an example of state change than a fundamental effect of a gas discharge. In one view, local heating starts thermionic emission -- the high currents/ion impacts are heating the electrodes. (In the Poulsen arc, the anode is metal and cooled with water while the carbon cathode is not cooled but rather rotated as it burns up.) Another arc discharge view is field emission.

Yes, there are books that claim the neon lamp oscillator is a negative resistance oscillator, but many of those books start with the static IV curve viewpoint. It's not a good or a clear example of negative resistance. Glrx (talk) 23:45, 10 January 2015 (UTC)

This has been discussed on Talk:Neon lamp. To make sure we're talking about the same things, the diagram at right shows what I think the curve is shaped like. There is a jump discontinuity (bg) as you say, but a portion of the "normal glow" curve (eg) (red) has negative resistance too. Solid black parts of the curve have positive resistance. The limit cycle (abcdea) of the simple RC neon lamp oscillator and its load line (blue) are shown, as given in many sources. This is just Neon bulb relaxation oscillator hysteresis curve.svg transposed. These are my concerns:
 
  • The jump discontinuity or instability (bg) as shown in most curves, is in the wrong direction to be responsible for the limit cycle oscillation. It is a voltage jump, most curves show the voltage switching between Vb and Vg at nearly constant current. This makes sense physically (avalanche multiplication and appearance of the cathode fall allows the gas to conduct a given current at a lower electrode voltage). But in the relaxation oscillator it is a current jump (dotted lines). When the voltage across the bulb rises to breakdown b, it doesn't drop along the discontinuity (be) as it would in a simple lamp; because of the capacitor the current jumps at almost constant voltage to c. When the voltage across the neon lamp declines from c to e, it doesn't jump back up to b, the current drops at constant voltage to a. During the limit cycle the state of the lamp never traverses the discontinuity (bg) (the "nonstatic" portion of the I-V curve). So the operation of the oscillator would be the same even if there were no discontinuity, even if there were a smooth curve between b and e (as there is in other negative resistances that are used to make relaxation oscillators).
  • You say: "...some other references describe a slight negative slope on the vertical portion of the second graph just below B, but that small curvature is not something that the conventional relaxation oscillator exploits." It seems to me it is essential. The negative resistance (NR) section is (eg). The load line (blue) represents the linear portion of the circuit:  . If the load line crosses the bulb's I-V curve at a point of positive resistance (positive slope, the solid black portion of the curve), that is a stable equilibrium point, and the circuit will not oscillate. You can see geometrically that, if (eg) has positive resistance, regardless of how wide in current the discontinuity (bg) is, the load line must intersect the curve at a point of positive resistance, either on the segment (cg) or (ab). The load line cannot reach the discontinuous region (bg) without also intersecting the stable curve. In that case there is no value of R for which the circuit will oscillate. As long as the discontinuity is a voltage (horizontal) jump, the segment (be) must have some region of negative resistance for the load line to pass through (it doesn't matter how "slight" the slope is), or the circuit cannot oscillate. This doesn't prove that neon lamps have negative resistance (the discontinuity can be some more complicated kind of jump) but it is certainly plausible that it has negative resistance before the jump, as shown in a number of the curves in the literature.
Every NR device works by a change in internal "state". A tunnel diode gets its NR from the change between ordinary majority carrier conduction and tunneling conduction. When an S-type (current controlled) NR like the neon lamp is driven by a voltage source, it will have hysteresis (sudden changes of internal state). That doesn't mean it doesn't have NR. The IMPATT diode, which has an I-V curve somewhat similar to a neon lamp with a discontinuity, works by a similar internal "breakdown" mechanism and increase in charge carriers. Going by the above arguments, a lot of other "negative resistance" devices besides the neon lamp, like the IMPATT, couldn't be called negative resistances. As far as I know, no one has ever suggested that.
Of course, what you or I think is immaterial. What matters is what WP:RSs say. There are plenty of reliable sources which say that gas discharges have NR, I gave 4 in Talk:Neon lamp and this article had 9. Here are some more: [1] (note graph 1.54, p. 63), [2], [3], [4], [5], [6], [7], [8] You haven't produced a single source that explicitly supports the above alternative theory. The difference between a jump discontinuity and a NR is pretty clear. If all the textbooks were wrong about gas discharges, I think someone would have pointed it out in the literature. So I don't see that WP:RSs support your position. Unless some pretty convincing contrary sources appear, it is obvious what the article must say about neon lamps. --ChetvornoTALK 00:17, 18 January 2015 (UTC)
In my opinion, the wholesale removal of gas discharge material from this article was ill-considered. Even if Glrx is correct and these are not genuine negative resistance devices, given the widespread coverage in sources we should still be covering it in our article. At worst we should be pointing out that this view is an error. But I am far from convinced that it is an error. Doubtless there are some circuit cases where the neon is being used as a simple switch and it would not be correct to view it as a negative resistor, but not in every case. I am seeing a lot of hits in IEEE Xplore from heavyweight papers backing up the idea of negative resistance of neons. Just to pick one, this paper is coauthored by Leon Chua of memristor fame, not someone likely to make errors of circuit theory. Sadly, my subscription to IEEE Xplore has expired, but I have this snippet from google "...with large source resistance R (approximately 1 MO) is attached to a shunt connection of neon bulb (ALCO-type BNE4R (with current-limiting resistor removed)) (acting as a current-controlled negative resistance), and capacitor C, forming the basic relaxation oscillator...". We can get hold of this paper through WP:LIBRARY if it is wanted for sourcing the article. Glrx, you need sources of at least equal stature before you can say what you want to say in the article. SpinningSpark 11:10, 18 January 2015 (UTC)
The discussion at Talk:Neon lamp#Why the neon lamp is a negative resistor and how it behaves when voltage driven went nowhere.
The IV diagram description above has a lot of handwaving in it. Is the IV characteristic static? Apparently not, because capacitance is invoked when one has to explain instantaneous jumps off the IV curve. What's happening in the tube? The heavy ions (slowly) reorganize rather than instantly jump. With insufficient voltage, new positive ions are not generated fast enough and the old ones neutralize or crash into the cathode. The description also starts from an assumption of a negative resistance region. I don’t dispute that there are self-consistent negative resistance explanations. The NR explanation is not the typical one used in RS.
Instead, let the supply voltage be above the breakdown voltage. Choose R so (1) the current supplied at the breakdown voltage is larger than the Townsend current (so we can charge to greater than the breakdown voltage) and (2) the current supplied at the sustaining voltage is less than the sustaining current (so the glow discharge is stopped). Such an explanation is not tied to a static IV curve; it is tied to the physics of the tube.
The state description is (in a practical sense) equivalent to modeling that thorny/unstable transition region with a stable negative differential resistor. (Maybe that's why Kennedy/Chua did it.) If one assumes a static IV curve and imposes continuity and believes in the mean value theorem, then there has to be a negative resistance region. If you don't assume a static IV curve or continuity, then there is no compulsion.
In solid state devices, the massive atoms in the crystal are not moving around. Yes, some carriers are slower/less mobile than others and stored charge can stick around a long time — especially in a PIN diode's intrinsic region. Neon is 40,000 times more massive than the lowly electron.
I don't buy into the notion that the above talk-section sources are RS for the topic. They do not seem to be the best sources. From the &q arguments, they resulted from searches for references that held the negative resistance viewpoint; that is a biased search.
  1. https://books.google.com/books?id=1BZVwUZLTkAC&pg=PA63&dq=neon+%22negative+resistance%22+%22glow+discharge%22 (note graph 1.54, p. 63); Lasers by A. E. Siegman. The book is about lasers, and it has little detailed information about gaseous conduction. It is passing mention. Furthermore, the application is not exploiting but rather avoiding any negative resistance characteristic. I’m not sure how much I should make of the diagram; the negative slope is more pronounced than I would expect, but there could be a lot more going on in the diagram. The gas laser graph shows a 14 W light bulb; it is not a hyperbola; higher currents mean higher powers and higher temperatures. It would make sense in a laser application for the graph to be a final value (after temperature equalization) rather than a quasi-instantaneous characteristic. An IV curve for a transistor is usually done at a constant junction temperature. The result after thermal runaway is something different. (An arc discharge can be a thermal runaway.)
  2. https://books.google.com/books?id=PfadZy35Wh0C&pg=PA567&dq=neon+%22negative+resistance%22 University Physics by George Arfken; this is a basic physics text with no apparent authority in electron physics and no discussion of the neon lamp's physics; it is passing mention.
  3. https://books.google.com/books?id=KYz1AAAAQBAJ&pg=PA235&dq=%22negative+resistance%22+%22glow+discharge%22 Atom, Laser and Spectroscopy by S. N. Thakur, D. K. Rai; also passing mention. Furthermore, mentioning negative resistance here is not needed. One needs a high voltage to achieve breakdown; once the tube is conducting, it exhibits a low resistance, so a current limiting resistor is needed. We don't connect zener diodes to voltage sources.
  4. https://books.google.com/books?id=Mdy2w-EWqEAC&pg=PA111&dq=neon+%22negative+resistance%22+%22glow+discharge%22 Handbook of Display Technology edited by Joseph A. Castellano; a handbook on display technology is hardly the place to get a definitive argument about gaseous conduction. It is also passing mention about negative resistance. The book does state the time to initiate the discharge (without priming) can take 100 μs. Further on, it makes the statement "The memory effect is realized by the fact that there are two stable states on the current–voltage characteristic." (By the way, GE's Glow Lamp Manual says it may take 300 μs to initiate a glow; up to 50 ms to deionize; and 6 μs to stabilize to a step change when conducting.)
  5. https://books.google.com/books?id=i_brZUv8JEYC&pg=PA256&dq=%22negative+resistance%22+%22glow+discharge%22 Vacuum Deposition onto Webs, Films and Foils by Charles Bishop. I'm not sure that a book on vacuum deposition is an appropriate venue to seek an expert on gaseous electronics, but the book does have a discussion of the physics. Figure 14.3 is promising (it may show carrier reorganization), but the linkage to the text is weak. The IV curve is static, there's no hysterisis, and the transition region is glossed over. The second paragraph of the transition region section seems confused about the cause. The arc discussion does point to a hotspot (drastic even destructive state change) going into other conduction modes.
  6. https://books.google.com/books?id=OKw1GJQ3bAQC&pg=PA44&dq=%22negative+resistance%22+%22glow+discharge%22 Industrial Plasma Engineering: Volume 2: Applications to ..., Volume 2 by J Reece Roth. Passing mention with difficult to interpret meaning. It also identifies a "mode transition" from an unstable arc to a stable thermal arc.
  7. https://books.google.com/books?id=I7Qi5vb2nB4C&pg=PA453&dq=%22negative+resistance%22+%22glow+discharge%22 Gaseous Electronics: Theory and Practice by Gorur Govinda Raju. Finally a source with a clearly significant title. The preview does not show figure 8.1, so I don't know B-C, but it sounds like the transition region. Section 8.2 is about conduction in a uniform field, but the transition region is all about the transition from the uniform field Townsend avalanche to the non-uniform field glow discharge. # https://books.google.com/books?id=xQfKWwvH42kC&pg=PA244&dq=%22negative+resistance%22+%22gas+discharge%22 Fundamentals of Light Sources and Lasers by Mark Csele. More passing mention.
A comment about passing mention. A serious secondary source will provide citations to primary sources.
It is not my burden to provide sources that say the negative resistance theory is discredited. To use the negative resistance claim, this article needs to cite to reliable sources that claim neon bulbs and gas discharge tubes are negative resistance devices. That view pops up in sources such as the above, but where does that view appear in reliable sources about applied electronics? Many reliable sources about physical electronics do not use the negative resistance explanation.
There are sources such as Reich that are RS about tube technology, use negative resistance as an explanation of tubes such as the dynatron but do not invoke negative resistance when discussing neon lamps or relaxation oscillators. Terman 1943 uses negative resistance for one flavor of magnetron (Magnetron Oscillators of the Negative Resistance or Dynatron Type, pp 527–528); Terman discusses a tetrode relaxation oscillator that uses "dynatron action" (so Terman is not afraid of using NR when all the carriers are fast electrons); Terman discusses a relaxation oscillator using a gas triode (thyratron) circuit (p 516) "commonly used to generate saw-tooth waves for sweep circuits of oscilloscopes"; that discussion does not mention negative resistance, but rather ionization that causes the grid "to lose control"; shut off happens when "there is not sufficient plate voltage to maintain ionization"; the "highest frequency obtainable in this way is limited by the deionization time of the gas in the tube" (ie, the slow carriers). Applied Electronics, McGraw Hill 1943, Chapter III is "Electrical Conduction through Vacuum, Gases, and Vapors". Its discussion of breakdown (cf 142) gives a carrier generation explanation of breakdown. It also covers glow discharges. A plot (fig. 13) on page 148 labels a breakdown, a transition region, and a flat-sloped normal glow region. Fig. 14 on the next page plots IV characteristics for 4 different glow-discharge tubes. The 2 neon sign tubes have a slight negative resistance over most of the graph; for example, one has 2 mA and 500 V going to 30 mA and 475 V (see heating possibility expressed above); the 2 W neon lamp near 0 mA is 70 V falling to and 0.25 mA and 55 V (this is in the first millimeter of a 100-mm wide graph; the graph does track the WP diagram above that has the negative resistance region outside the hysterisis portion). The book separates two classes of oscillators: negative resistance and feedback oscillators (p 597). It then offers another oscillator classification as sinusoidal or relaxation oscillators. Relaxation oscillators "are characterized by a sudden change, or relaxation, from one state of unstable equilibrium to another." These books are serious texts with footnotes to original sources.
I don’t know what Penning or Loeb say; I’m not near the library right now. Another vacuum tube book clearly states that an IV characteristic is not static, but I doubt I could locate that ref again.
See also
  • Petrović, Z. Lj.; Phelps, A. V. (January 1992), Optical and Electrical Characteristics of the Cathode Fall, Technical Report, Wright-Patterson Air Force Base, OH: Wright Laboratory, Air Force Systems Command, WL-TR-91-2094, DTIC AD-A249 010, which show oscillatory instability in several operating regions of glow discharges. The source does state that "This region is inaccessible because of the negative differential resistance behavior of the discharge in which the use of too small a series resistance results in a jump of the current over the region." It is also not lost on me that oscillation could imply negative resistance, but in this instance the oscillation is probably the failure to settle into a stable carrier configuration. Sometimes one gets striations in gas discharges.
The Kennedy/Chua reference is dubious. The topic is about Van der Pol oscillators, and the abstract (I don't have the paper either) states:
Experimental confirmation has been made on a driven relaxation oscillator circuit, first presented by Van der Pol, of the period adding route to chaos. The nonlinear element in the circuit is a neon bulb, modeled by a three-segment piecewise-linear current-controlled resistor. A simple nonlinear circuit model has been used to reproduce in simulations the experimentally-observed period-adding phenomenon.
The paper is not about the physics of a neon oscillator but rather a simple model using a "three-segment piecewise-linear current-controlled resistor" for simulations. Adopting a negative resistance oscillator model says nothing about the actual physics.
Discharge tubes do not need to be discussed in this article.
Glrx (talk) 23:34, 20 January 2015 (UTC)
Ok, you've got a bunch of criticisms of sources that say neons have negative resistance, but do you have any sources that actually say the negative resistance viewpoint is wrong. SpinningSpark 00:08, 21 January 2015 (UTC)
Yes, it seems to me that's the first prerequisite. The fact that an author doesn't happen to mention negative resistance in his analysis of gas discharge does not mean he disagrees with the term - inferring that is WP:SYNTHESIS. --ChetvornoTALK 10:44, 21 January 2015 (UTC)
@Spinningspark: Demanding a source that says negative resistance viewpoint is incorrect is asking for evidence to prove a negative. The appropriate viewpoint for me is to look at how reliable sources treat the topic. If the reliable sources don't raise negative resistance, then WP shouldn't either. My criticism of the sources above is primarily their tangential / passing mention. Laser physics might be interesting, but it doesn't mean the author is a reliable source or authority for gaseous conduction.
@Chetvorno: Your comment about synthesis is misplaced. I'm pointing out that serious reliable sources are not invoking negative resistance.
Herbert J. Reich, Theory and Application of Electron Tubes, second edition, McGraw-Hill 1944. I'll recommend chapter 11, "Electrical Conduction in Gases"
Reich is the reliable secondary source WP seeks. He collates secondary sources.
Reich, fig 11-1, page 417:
As the voltage is increase, a value is reached, as at b, at which the current again begins to rise. If the electrode spacing is very small and the pressure sufficiently low, the current can be increased beyond b only by increase of voltage, and the characteristic is of the form shown by the dashed curve bm. With electode spacing and pressure used in most glow-discharge tubes, on the other hand, a current is reached at c, called the threshold current, at which the current begins to rise abruptly without further increase of voltage. The threshold current is still of the order of one or two microamperes. If the external circuit resistance is low, the voltage of the discharge remains practically constant, and the current jumps to a high value (milliamperes or even amperes), corresponding to n. If the external circuit is such as to prevent the current from rising abruptly, then the voltage drops abruptly to some lower value, as at d. The value of the current at d, and the path alogn which the change takes place, appear to depend almost entirely upon the external circuit. Experimental difficulties, such as the occurrence of relaxation oscillations, have so far prevented a complete study of the characteristic immediately beyond point c, but those experiments which have been performed appear to indicate that if the terminal voltage could be reduced rapidly enough by increase of circuit resistance or decrease of applied voltage, the current at point d would be the same as that at point c.
Reich, page 418, explains voltage drop with increasing current (arc discharge) as a temperature change at the cathode (a state change):
In the vicinity of g, however, the current is so high that, if it is maintained for an appreciable time, the cathode becomes hot enough to emit electrons. The thermionic emission reduces the voltage drop through the tube in a manner that will be explained in Sec. 11-14, causing further increase of current and greater emission.
Reich, page 418:
The exact predetermination of the behavior of a particular glow-discharge tube is difficult, if not impossible, because a given tube does not have a single current-voltage characteristic, but an infinite number of characteristics. The shape of the characteristic depends upon gas pressure, electrode temperature, and age of the tube; upon the amount of ionization remaining from previous discharges; upon the initial cathode emission, which varies with the cathode illumination; and upon the strength of other ionizing agents in the gas or container. A characteristic obtained with steady applied voltages, of which the curve of Fig. 11-1 is a typical example, is called a static characteristic. Characteristics obtained with varying voltages and currents are called dynamic characteristics.
Reich is not explicitly stating that "negative resistance" is wrong, but he is stating that a single static IV curve is folly, and he gives state change explanations for IV characteristics that others might label "negative resistance".
Reich explains that the gas discharge takes times to set up. Page 427, "11-7. Time Required for Ignition".
The field distribution changes. Reich p 429:
11-9. Breakdown.—As soon as appreciable curret flows, formation of space charge in the vicinity of the cathode causes almost the entire applied voltage, which was initially distributed uniformly over the whole cathode-to-anode distance, to become concentrated in th cathode dark space.
Reich page 431 explains how the space charge affects characteristics.
Reich page 433–434 describes dynamic characteristics he was involved with taking.
Reich page 435 has some nice numbered points about dynamic characteristics. For example, point 3:
3. When the current is decreased abruptly, it does not follow the static characteristic but, instead, a slightly curved path to the origin. This is explained if it is assumed that the time required for deionization greatly exceeds the time taken for the current to fall to zero. The increase in tube resistance accompanying deionization is evidenced by the decrease in slope of the characteristic as the current falls.
Reich page 439:
High-current-density glows may be maintained for time intervals that are too short to allow the cathode to heat to the temperature required for emission....
Glrx (talk) 03:35, 8 December 2015 (UTC)
In answer to your criticism that I am calling for sources "to prove a negative"; that would be valid if there were not already sources asserting the positive. But there are, so sources saying they are wrong are needed before Wikipedia can say they are wrong. The best you could say is that some sources do not invoke negative resistance in their analysis of gas discharge tubes. But why should they? Negative resistance is not a fundamental property of the physics of the tube. It is a property relevant to the analysis of an external circuit. That is why the Chua paper, from an expert in circuit analysis, is relevant here as a reliable source.
I am not seeing in your cites that Reich is saying "a single static IV curve is folly". Indeed, he seems to be saying just the opposite, that a static IV plot is possible. If he thinks it is impossible, why did he publish such a plot? What he does say is that there is more than a single dynamic IV plot because there are many dynamic variables. It is nevertheless still possible to make a plot for a given set of conditions. SpinningSpark 10:36, 8 December 2015 (UTC)
Glrx, re: "prove a negative"; citing a single 70 year old tube book while rejecting the 8 contemporary sources I gave above seems like pretty extreme WP:CHERRYPICKING. But the crucial point is that even your chosen source does not support your position. Reich does not say that gas discharge tubes do not have negative resistance - he simply fails to mention it. Spinningspark's suggestion that this is because "negative resistance" is an external circuit description which is not relevant to Reich's analysis of the physics sounds plausible to me. Quoting large amounts of text in an effort to demonstrate something that is not stated in the text is not only WP:SYNTHESIS, it is a very tenuous synthesis. The term "negative resistance" is very widely used in electrical engineering sources to describe the IV curve of gas discharge tubes, whether or not you accept these as WP:RSs. If experts believed this was a misuse of the term, someone, somewhere in the literature, would have said so. You have not cited a single source that says that. So I don't see that there is any support for your position. --ChetvornoTALK 13:15, 8 December 2015 (UTC)
@Spinningspark:
Reich publishes a static IV curve, but he tells us that it is a static curve and that the dynamic story is different. He offers plots showing that the static IV characteristics don't apply. Compare to the IV characteristic of a transistor; the usual case (ignoring transit time) allows us to use the static IV characteristic as a model; dynamics are covered by some small signal linear capacitors. Gas tubes, especially ones where some authors will invoke negative resistance, are not following the static IV characteristic and are not using small-signal operation.
The negative resistance viewpoint of gaseous conduction is naive. I'm not saying WP should make that statement because sources don't make that assessment; they have no reason to make such a statement. I'm saying WP should be silent on the negative resistance explanation; if it does invoke negative resistance, then it should balance that with authors that do not invoke negative resistance. If we go to the sources that actually address the physics, they either offer explanations with clear mechanisms (e.g., transition to thermionic or field emission in an arc discharge) or claim the mechanism is not clear. They do not use a static IV curve and the mean value theorem to prove negative resistance. BTW, Reich's static IV is careful in a lot of areas, and includes discontinuities in the plot and axes.
In addition, there are many sources that describe dark current conduction with no appreciable space charge, the velocity differences between electrons and positive ions, and the glow discharge with its cathode fall. It takes time to reorganize the heavy positive ions.
Chua may be a circuit theory expert, but is he an expert on gaseous conduction? As stated above, the abstract suggests that the paper is about Van der Pol oscillators rather than gaseous conduction and that Chua isn't using an actual neon lamp but rather "a three-segment piecewise-linear current-controlled resistor". I don't have the paper, but does it delve into the neon lamp at all? The Van der Pol issue could just as easily be addressed with "a three-segment piecewise-linear current-controlled resistor" model of a tunnel diode -- something that none of us would dispute is a negative resistance device. Chua doesn't rise or fall on a bad model of a neon lamp. BTW, I'd be curious about where he set the break points -- the neon lamp breakdown is at a very low current. File:Doutnavka.svg suggests that breakdown is at 10 ma.;
I am confused by your comment that negative resistance is not a property of the tube but may be used as a model for circuit design. If negative resistance is not a propery of the tube, then why should it be invoked at all?
@Chetvorno: I don't know what to say. Gaseous conduction was a research topic in the early 20th century. Plasma physics for a few decades after that. Gaseous conduction is not a big research topic today because it has been mined out. Similarly, Newtonian physics is not a significant research topic today even if Feynman had some fun in the 1970s. The books that discussed gaseous conduction will be old. There's little reason for modern sources to address vacuum tube technology because vacuum tubes have mostly been supplanted by semiconductors. IIRC, you use a lot of old sources for old-technology radio detectors. Neon lamps are old technology. The physics hasn't changed, so the sources are still valid.
I don't see quoting Reich as WP:CHERRYPICKING. I am not selecting portions of Reich that favor me and ignoring sections that do not. Maybe I'm over-the-top with the static IV "folly" statement, but Reich is clearly pointing out that a neon lamp does not have a single IV curve.
As an editor, I believe I am entitled to comment on weight. Authors such as Reich and Terman have substantial weight.
You gave a list of references above, and I commented that the list was biased because it was the result of a search for negative resistance. Consequently, it would exclude references that did not mention negative resistance. Beyond that issue, most of the references were passing mention or only tangentially concerned with the topic; they were not surveys of the field. Reich is a survey of the field. The references in your list have little weight, and a lot of references with little weight do not add up to a lot of weight. Where the references had more weight, I took more time to address their comments. Laser tubes, for example, can reasonably present a static IV plot with a negative slope, but that does not mean they are negative resistance devices. I don't consider a negative-temp-coef thermistor a negative resistance device; it is a device that has more state than just current or voltage.
Your RS reasoning is backwards. If a source is not an RS, then WP does not care what it says. A published book does not automatically have the rank of RS for anything that it says. I've criticized several claimed RSs above; many titles were not on point; many comments were passing mention. I don't see a defense of those sources. More importantly, I don't see citations to sources that address the field of gaseous conduction and invoke negative resistance. The best source I've seen for negative resistance has been the GE manual, and even that book waffles about the transition region (Figure 1.1, page 1, E–F; page 2, an "unstable region", "this region is often referred to as the negative resistance region").
My purpose in quoting long sections of Reich is to offer a serious source's explanation of the physics.
Glrx (talk) 19:33, 8 December 2015 (UTC)
In their paper, Kennedy and Chua are not just constructing a piecewise linear model in an entirely theoretical environment. They actually built a neon bulb oscillator and observed its behaviour. They were interested in the chaotic transitions of the oscillator between sub-frequencies. Their model accurately followed the experimental results,

Thus, in our simulation, we have accurately modeled teh dynamics of the system under investigation and have consequently succeeded in reproducing those period-adding phenomena present in the original circuit

— Kennedy and Chua, p. 977
If the negative resistance model is not a valid circuit model of the neon lamp, then this would be an extraordinary result. The coincidence would be unbelievable. I contend that it is not a coincidence. SpinningSpark 21:46, 8 December 2015 (UTC)
I'll have to look at the paper. Glrx (talk) 00:30, 11 December 2015 (UTC)
@Spinningspark and Chetvorno: Sorry for taking so much time to pull the ref.
Kennedy and Chua's CAS vol 33 issue 10, October 1986, pages 974–980, paper is irrelevant. They do not mention gaseous conduction at all. There is no discussion of the bulb's physics. KC are interested in "period-adding phenomena" rather than negative resistance. The only significance of neon lamp is that Van der Pol and other authors used a sinewave driven neon relaxation oscillator. The paper is muddled in another sense. The interesting issue is supposedly chaos (the "noise" that Van Der Pol skipped over), but KC developed a deterministic model so they could simulate something that does not have the nuisance of comsic-ray coin flips. Yes, there's subharmonic locking, but that's not chaos; analog TVs used that trick twice over.
The article claims:
It should be noted that a neon bulb is a very complicated device, yet we have been able to duplicate its dynamic behavior over the frequency range of interest (below 1 kHz) using the simplest possible model[10]. This confirms our belief that a neon bulb may be realistically modeled at low frequencies by a series connection of inductance (which we have indicated is an essential component of the dynamic model) and current-controlled nonlinear resistor.
The goal is model simplicity and not model accuracy. It is sufficient to duplicate dynamic behavior. The paper does not attempt to show that neon lamps are negative resistance devices. It only claims a negative resistance model will duplicate low frequency dynamic behavior.
The model is not related to the physics. "The neon bulb has been modeled by a current-controlled resistor with three-segment piecewise linear I-V characteristic, ...." The model is just by fiat; there's no explanation of why it is chosen. They do give a measured static characteric in figure 7. They also plot their model in figure 7, and the model just copies some gross characteristics. The exponential shapes have been thrown out. The goal is not accuracy, but rather making the simplest model. Also, there is no discussion about how the neon bulb measurements were made — something that has frustrated people who try to make such measurements. Even the GE manual raises the instability issue. Not a problem for KC: their VIC is stable and continuous from the beginning.
The article has some horrible nonsense wrt the inductor:
A parasitic inductance L, has been included in series with the current-controlled resistor in the neon bulb model to account for the element's dynamic behavior. (The circuit model is very sensitive to the value of L, (chosen to be 1 pH); too high a value of parasitic inductance reduces the widths of the transition regions between periods (n - l)T and nT.) This inductance is an essential part of the neon bulb dynamic model since its I-V characteristic is nonmonotonic and current-controlled. Note that the state equation of the circuit does not exist if L, is not included[6].
At first blush, adding some inductance could make physical sense because the neon bulb's carriers do not instantly vanish. But KC do not tie anything to physical phenomena. They just had to insert the inductor to the simulation work. Physically, the smallness and the sensitivity of the inductance destroys the validity of the model. A one-pH inductance would be swamped by real-world wire inductances. There's a lot more than 1 pH in series with a neon bulb. A rule of thumb is wire inductance is 10 nH per inch; the model inductance suggests a length of 0.0001 inches (2.5 μm). KC tell us the simulation doesn't work if the value is significantly larger. An NE2's pigtails will have a significantly larger inductance.
The inductor raises the spectre of Bob Pease's distruct of SPICE in reverse. Pease didn't like adding parasitic components to make SPICE converge; apparently KC have no qualms about adding such components. Yes, KC make some justification about the inductor being needed to increase the system order, but that does not make their model a real-world one. They really don't care about the real world.
As to the "extraordinary result" comment, KC admit in the paper that a hysterisis model achieves the same result:
Newcomb [ll] has observed chaos in an apparently second-order autonomous circuit, where the nonlinear element is described not by a single-valued function, but rather by one which exhibits hysteresis. Such a hysteretic component is in fact a dynamic element requiring at least one additional state variable before the circuit can be modeled by a system of ordinary differential equations[12].
The paper is irrelevant wrt negative resistance and gaseous conduction. Gaseous conduction is not Chua's field, and the article is an unreliable source for our purposes.
Glrx (talk) 22:37, 8 January 2016 (UTC)

Cosmetic and other edits

Latest comment: 7 years ago7 comments5 people in discussion

I support User:Spinningspark's revert of User:A876's extensive changes. I don't think any editor should have to go through and manually fix such an extensive change (almost 10K characters). It is enough that some portion of the edit have errors in it. For example, XML requires that attributes be surrounded by quotation marks, so every edit that changed <ref name="foo"> to <ref name=foo> is a poor edit even though such edits work on most XML parsers. We don't assign tasks to other editors; we are volunteers here. Spinningspark need not save edits that fix some subject-verb disagreements (transistor/transistors), some reasonable WL collapses, and appropriate hyphenation. I also find it troublesome that one would defend cosmetic edits ("revert-all WASTES work. restoring ref-errors IS harm. "cosmetic" is NO harm, encourages editors. "potential harm" ≠ harm. there is no "I" in Wikipedia. byp red reveals common target article."). Furthermore, style-only edits should not be done: e.g., changing [[Gas discharge|discharge through gases]] to [[gas discharge|discharge through gases]] is pointless (and why did Hartley go the other way?). Bypassing redirects can violate WP:NOTBROKEN. I think the extensive edit had some reasonable changes in it, but it was presented as an all or nothing affair. Glrx (talk) 23:18, 5 January 2017 (UTC)

Reaction:
  1. "I support Spinningspark's revert ..." (citing Spinningspark's second revert). I find this unsolicited tag-team, ahead even of Spinningspark's comments, scary.
  2. "I don't think any editor should have to go through and manually fix such an extensive change ....." I don't either, but almost nothing needed fixing. Spinningspark's only real objection was my adding unsourced material, which he did not even mention. All Spinningspark had to do was remove the unsourced material and summarize "Sorry, can't keep unsourced material in a good article." (though sourcing it would have been nicer).
  3. "For example, XML requires that attributes be surrounded by quotation marks ..." What possible relevance could that have here? Wikipedia markup is not XML. "Quotation marks are optional if the only characters used are letters A–Z, a–z, digits 0–9, and the symbols ! $ % & ( ) * , - . : ; < @ [ ] ^ _ ` { | }" (See WP:NAMEDREFS.) "... every edit that changed <ref name="foo"> to <ref name=foo> is a poor edit ..." No, it isn't. "... even though such edits work ..." So what is your problem?
  4. "Spinningspark need not [preserve] edits that fix ..." Well, if they "fix", that sounds like a reason to leave them alone.
  5. You quoted my edit summary, but not Spinningspark's summary that I reacted to. I find that lawyering. Spinningspark said "Reverted good faith edits by A876: Most of that edit is purely cosmetic, but some is potentially harmful. Some of the redirects should not be bypassed. There is no good reason for removing quotes from ref names. Sorry, I am not going to p..." I find that summary incorrect and autocratic. I replied honestly (in my edit summary) when I put the same edits back in, that no actual reason was given for reversion: "revert-all WASTES work." (Would you disagree?) "restoring referrors IS harm." (Would you disagree?) "'cosmetic' is NO harm, encourages editors." (Would you disagree? Undoing cosmetic is an even bigger waste: I didn't break anything; pointy.) "potential harm' ≠ harm." (damn right. I didn't break anything.) "there is no 'I' in Wikipedia." (Reacting to the incomplete "Sorry, I am not going to p...". Does someone sit above others?) "byp red reveals common target article." (In one case.) Also you did not quote the summary of Spinningspark's second revert of the same edit (again without the real explanation, unsourced material): "Reverted good faith edits by A876 (talk): I object to this edit, please follow WP:BRD and take it to talk." (there's that "I" again.) (the "R" in WP:BRD is not a prescription.)
  6. "Furthermore, style-only edits should not be done: ..." So? It was not a style-only edit, though there was [much] incidental clean-up of inconsistency. If style cleanup is not done it will either remain wanting, or else be done later anyway (sooner being better). Whether cleanup is annoying or hard to excuse, unnecessarily putting back cruft is atrocious.
  7. "e.g., changing [Gas discharge|discharge through gases] to [gas discharge|discharge through gases] is pointless..." No, it isn't. Piped links are supposed to match the casing of their context, for readability while editing the markup (for those who still edit markup). When [Gas...] is neither a proper noun nor beginning a sentence, is should be [gas...]. If someone did not do it the sensible way, adjusting it for the better is not pointless, it is constructive, and therefore not wrong.
  8. "(and why did Hartley go the other way?)" Why, because I'm an idiot and a hypocrite, of course. Seriously, you couldn't figure it out? Are you trying that hard to hang me? I changed the first "Hartley" from "hartley" in this: (approx)"how feedback oscillators such as [Hartley oscillator|Hartley] or [Colpitts oscillator]s work". Same principle, match the casing that it would have in context. Hartley is proper noun that is always capitalized. If you would make me wrong for fixing that, then I suppose a link like [richard Nixon] would be to your liking if not preference.
  9. "Bypassing redirects can violate WP:NOTBROKEN." Yes, maybe it can. Now what? I try to be sensible about it. Redirects can be distracting on the target page. Very bad piped links are distracting too. See WP:EASTEREGG. A link like [FBI] works with redirect, but a piped link like [Federal Bureau of Investigation|FBI] is better because the user can see on hovering where the link will go (try it: FBI), rather than have to follow it just to get the expansion of the acronym.
  10. "I think the extensive edit had some reasonable changes in it" (thanks) "but it was presented as an all-or-nothing affair." Yes I kind-of do that. If formatting and style were better regarded and standardized, a robot could handle them before or after every edit. But they aren't. Formatting and style are nice to have, but editing only formatting and style is already deemed wasteful, and I agree. So I try to roll in formatting and style edits whenever I have "real" edits; otherwise, tell me, how will they ever get done? This time I took a chance: I did lots of formatting and style, some wikignomish small edits, and hardly any "substantial" edits, and (oops) an unsourced addition. To an article that is possibly better-watched, this "good article" (a medal which seems unmerited, given that it overlooks the most obvious and intuitive application of negative resistance, cancelling out positive resistance of a power cable or motor winding).
  11. It's hard to imagine devoting such time and effort to tearing down an editor, lawyerishly objecting to petty disagreement to the point of not even getting around to stating the legitimate objection. I find most of the edit summaries and the comments here demoralizing and bitey. I am appalled. -A876 (talk) 01:56, 19 February 2017 (UTC)
Just for the record, here are some more things I found objectionable. I am baffled why this editor wants to decapitalize piped links. Bypassing redirects is not always a good thing. For instance Electrical resistance may actually become a standalone article one day (as it once was) so its best to leave links that actually refer to resistance pointing to the redirect. Same goes for conductance. I personally don't especially have a problem with removing whitespace from the ref templates, but presumably the editors who put it in thought it made the edit window more readable. It is just not on for editors that are not primarily content creators to impose a different way of working. That just makes life difficult for the content creators if it is not reverted. That applies to the quotes on ref ids as well. Either the editors have to now change to the new way, or if they don't they risk being criticised for inconsistent formatting at article reviews. If A876 was going to do some major work on the article and worked in a different way there might be a case for a change, but that is not happening here. The only thing of substance added, as far as I could find was sentence on motor speed control. And that was uncited, so if for nothing else, I reverted for adding uncited material. That puts A876 in breach of WP:V, a major policy, for putting it back without providing a ref. SpinningSpark 23:41, 5 January 2017 (UTC)
Reaction:
  1. "I am baffled why this editor wants to decapitalize piped links." (Again with the "I".) Does acceptability of edits depend on whether you understand why? Links work capitalized or not. Why? That allows article names in normal links to take the case that they would have in context, without needing piped links just to handle capitalization. Trivial example: "[Junk] is a form of [junk]." Both links go directly to the article Junk. The same feature allows article names in piped links to take the case that they would have in context, or the opposite case if someone chooses or defaults. But why is using the contextual case better than the opposite case? Because it makes better reading than a CamelCase sentence in the markup. Trivial example: "[Junk (scrap)|Junk] is a form of [junk (scrap)|junk]." That is the preferred form. (Even if I can't re-find the guideline that recommended it.) Naturally, the contrary form works just as fabulously: "[junk (scrap)|Junk] is a form of [Junk (scrap)|junk]." Would you really prefer that? Would you defend that form? Would you get upset if someone adjusted it? Would you put down someone who corrected it? Beyond that, I have to ask, were you really "baffled why this editor wants to decapitalize piped links"? Besides looking at diffs, you must surely have edited markup, but you really couldn't figure out why I would make such a change? Then I hope this was informative.
  2. "Electrical resistance may actually become a standalone article one day (as it once was)..." Probably never, but point taken. [[[Elastance]] (inverse of capacitance) and admittance (inverse of impedance) still have articles. It was a little overreaching, but it was in reaction to "[Electrical conductance|Conductance] is the reciprocal of [electrical resistance|resistance]" - I found it annoying that both links go to [Electrical resistance and conductance] without warning.
  3. "I personally don't especially have a problem with removing whitespace from the ref templates, but presumably the editors who put it in thought it made the edit window more readable." If I come along and I'm smarter than all the other editors, why, I'll indent everything TWO spaces instead of one. That way, if someone does search-and-replace for two consecutive spaces (pointless noise that usually only affects paragraphs), now they get a thousand "false" hits. That's progress? No. More like sabotage. It has to go. Like ridiculous content, ridiculous formatting is up for editing. "If you don't want your writing to be edited mercilessly and redistributed at will, then don't submit it."
  4. "It is just not on for editors that are not primarily content creators to impose a different way of working." Oh, now I get it. There are classes of editors. (Not in any official policies, but I should have suspected.) I was not "impos[ing] a different way of working", I was opposing an unnecessary new way of working, one that can't be found if searching a hundred other articles. A way that wouldn't tragically be possible if the markup had complete standards and/or was self-correcting to prevent all the cruft-puffers who think their idea of breaking and tabbing and indenting is so much smarter than what works everywhere else, for everyone else. "That just makes life difficult for the content creators if it is not reverted." (Again with my scabby stupidity impairing the "real" editors.) No, it deters them from bad habits that should not spread. Let them work on normal pages, before they go indenting and tabifying and inserting random spaces into every paragraph of every article.
  5. "That applies to the quotes on ref ids as well. Either the editors have to now change to the new way, or if they don't they risk being criticised for inconsistent formatting at article reviews." Don't accuse me of making a "new way". I was pulling toward the old way. (Has any editor been "criticised for inconsistent formatting"?) (Is there such a thing as an "article review"? A link might be deserved.)
  6. "if for nothing else, I reverted for adding uncited material" And there it finally is. After two reverts, at the end of the talk-page lecture, you finally give a valid reason for editing. I'm so glad you got round to it. You could have saved a lot of effort by putting it in the first edit summary, instead of a rant about things that don't matter ("cosmetic", "potentially harmful", "no good reason", and "Sorry, I am not going to p..."). Very, very discouraging. -A876 (talk) 01:56, 19 February 2017 (UTC)
@A876: Thank you very much for removing [9] the illegal links in citation templates; that was my screwup (an error I also committed on numerous other pages). As for the other edits, although your motives were good, I support Spinningspark's and Glrx's remarks above. --ChetvornoTALK 01:43, 6 January 2017 (UTC)
I'm okay with parts of what they did and said, but I could never provide drive-by "support" for such foot-wiping. -A876 (talk) 01:56, 19 February 2017 (UTC)
Being reverted is standard procedure at Wikipedia—it should not evoke walls of text, and reactions should not include claims of tag teaming or foot wiping. Further responses are not needed. Johnuniq (talk) 02:54, 19 February 2017 (UTC)

The Deborah Chung paper

Latest comment: 7 years ago6 comments4 people in discussion

@Glrx: What was your objection to including the example of the Chung paper? I was trying to show the reaction of the electrical engineering profession to a report of negative absolute resistance. I thought it was a good example.

A negative absolute resistance (as opposed to a negative differential resistance) produces electric power, so negative absolute resistance in a passive material (her carbon fibers) is equivalent to "perpetual motion"; energy from nothing. In the news sources I gave: [10], [11] the scientific community quite properly reacted to Chung's paper by making it clear that that is impossible. Primary research often is in error; the conclusion of mainstream scientists was that her observation of negative resistance must have been due either to some small "active" process in the material; a contact potential or electrochemical reaction which produced a potential difference, or a defective measurement technique. As far as I can tell, the cause of her negative resistance measurement hasn't been resolved yet, but that doesn't mean anyone believes carbon fibers can produce energy from nothing. The point of the example is the reaction of the scientific community: negative absolute resistance in passive materials violates the laws of thermodynamics. --ChetvornoTALK 02:52, 28 March 2017 (UTC)

I'm fine with no perpetual motion references, but an encyclopedia isn't interested in small details. There's no point in calling attention to one paper. The rebuttal refs are not strong (judgment from an abstract rather than the paper). Your comments about no resolution make the issue even cloudier. There's a touch of WP:SYN. Glrx (talk) 03:28, 28 March 2017 (UTC)
I agree with Glrx—articles should avoid news-of-the-day, particularly when it enters WP:REDFLAG territory. This article is about what negative resistance has meant for over fifty years, not breakthroughs that might be valid. Johnuniq (talk) 03:47, 28 March 2017 (UTC)
That was the whole point of the example, Johnuniq. The content Glrx removed said:
"For example, in 1998 materials scientist Deborah Chung reported finding apparent negative static resistance in carbon fiber composites. Her paper was met with disbelief from scientists.[citations] Her observations have not been repeated by any reputable lab."
Negative resistance means a violation of the 1st or 2nd law of thermodynamics. That's not "news-of-the-day", it's been accepted a lot longer than 50 years, since 1892. So reputable scientists rejected Chung's claim - exceptional claims require exceptional proof. The text nowhere says the claim is valid, where is the WP:REDFLAG? The text supports everything you said above.
Glrx, the violation of the laws of thermodynamics is not a "small detail". That's why Chung's obscure material science paper was the subject of a Los Angeles Times article and an editorial in the journal of the Electric Power Research Institute. The refs quote plenty of "rebuttals" from scientists: Cetin Cetinkaya:"Physically, that's not possible." Steve Kivelson: "It's impossible." Brendt Fultz: "...it's violating one of the two laws of thermodynamics." If by "rebuttals" you mean experimental evidence contradicting Chung, I suspect this case is pretty typical of reported 2nd Law violations. It's been 20 years and Chung's data has not been repeated, AFAIK. For this "exceptional claim" the burden is on Chung's supporters to provide more evidence than a single experiment, before the scientific community takes them seriously. They haven't been able to do that, so it's pretty clear that her observation was a fluke, like many, many "unrepeatable results" before it.
And where is the WP:SYN in the text I added? --ChetvornoTALK 11:02, 28 March 2017 (UTC)
I have to agree with others that this is a bit out of place. It's a bit like introducing perpetual motion into the engine article only to then shoot it down (although I'm not suggesting that Chung is a fringe crackpot). It's not as if more sources were needed to support the article text. There are already more than enough, too many it could be argued. It's also somewat odd to bury the discussion in the references. If we are going to discuss it here it should be in visible text in the body of the article. But I really think Chung's page is a more appropriate place, or perhaps the perpetual motion page. SpinningSpark 13:05, 28 March 2017 (UTC)
Actually the sources for this section are particularly weak, which is why I included so many. Spinningspark, I certainly disagree with your argument that a report of negative resistance is "out of place" in the Negative resistance article. The reason I "buried" the discussion in the references is the same reason that you want it omitted altogether. The scientific community didn't believe Chung's claim, and her observations haven't been repeated. Discussing it in the article would give it WP:UNDUE WEIGHT; give the erroneous impression it was considered seriously; it would be WP:REDFLAG, as Johnuniq said. I thought if it was presented correctly, as a footnote, readers would see it as it is: a single irreproducible result contradicting a 400 year old law of physics, and so not to be given much weight.
However, I thought about your (collective) objections, and I guess you all have a point. Including the Chung claim in the article at all, without a clear refutation, is inevitably going to give some general readers the wrong idea, be UNDUE WEIGHT and REDFLAG. I accept Glrx's revert. --ChetvornoTALK 01:45, 29 March 2017 (UTC)

Recent revert

Latest comment: 6 years ago7 comments4 people in discussion

@Glrx: what is your objection to the clause? Is it just the word "electronics" or the entire addition? --ChetvornoTALK 14:35, 30 April 2017 (UTC)

The entire clause. Many complaints. Let's start with a source for the statement. Glrx (talk) 20:23, 30 April 2017 (UTC)
Most of these are already cited in the "Active resistors" section. Also, as explained in that section, it can be seen from the equation for the input resistance of a positive feedback amplifier   that if the loop gain   (the regeneration) is greater than one, the input resistance will be a negative number. --ChetvornoTALK 07:53, 1 May 2017 (UTC)
I think the issue is that active resistor is not synonymous with positive feedback. Sufficiently large positive feedback will give rise to negative resistance, but the terms are not sysnonymous. It is not even true that negative reistance iff positive feedback, since low positive feedback gives positive resistance (although it always reduces the pre-existing resistance). I would also question the implication that active resistor implies negative resistance. A resistance generated through negative feedback is still an active circuit to my mind, but the resistance is positive in that case. One can also produce a resistance with an active circuit without any feedback at all. SpinningSpark 12:49, 1 May 2017 (UTC)
@Spinningspark: The sentence Glrx reverted
"In circuit theory these are called "active resistors", but in electronics this property is more often just called regeneration or positive feedback."
does not exactly say active resistance is synonymous with positive feedback. It just says because more specific terms for this property like "active resistance" are not used much in electronics literature yet, this behavior is just lumped under the terms "regeneration" or "positive feedback". Also, since as you say positive feedback (regeneration) always results in a lower resistance than if there were no feedback, in that sense any amount of positive feedback adds "negative resistance" to a circuit. I wouldn't mind the above sentence being edited to make it clearer, but it should not just be deleted. It's important to explain to readers that they're not usually going to find this kind of negative resistance called "negative resistance" or "active resistor" in the literature. --ChetvornoTALK 16:15, 1 May 2017 (UTC)
@Spinningspark: Re "I would also question the implication that active resistor implies negative resistance". I agree. The term "active resistor" has several other meanings in electronics [12], [13] such as a transistor with negative feedback applied to give it high (positive) resistance, used as an active load for another transistor [14], [15]. That should probably be noted in the section.--ChetvornoTALK 16:15, 1 May 2017 (UTC)
Proper and correct term is "active load"... let us not add more to the confusion — Preceding unsigned comment added by Hudavendigar (talk • contribs) 19:32, 8 June 2018 (UTC)
Latest comment: 4 years ago5 comments4 people in discussion

@Thomas H. White: the urls you are trying to change gbook links are still snippet view to me so I have reverted again. Why this determination to change the links to Google? Do you own shares? The previous links were perfectly servicable and freely accessible. The issue may be that gbooks access is country related. But whatever, it is pointless to change working links. At best there is no advantage, and at worst you will break something. SpinningSpark 23:39, 27 January 2020 (UTC)

I was not aware that certain people cannot access all of the public domain material on Google Books. It appears that you are located in the U.K., so apparently through either oversight or by Google policy some material in the public domain is not being made available to one or more foreign countries. However, until now I was not aware of this. I generally prefer to use links to Hathitrust.org rather than Google Books, but in this case the material does not appear to be available at that site. One of the links in question is a transcription I have on my own website, earlyradiohistory.us, which at the time I added it was not in the public domain. I have a general policy of updating these links when the material enters the public domain, because for research purposes it is preferable to link to the original document. Also, since I do not plan to live forever, my webpage will eventually disappear. The other link was to a PDF file, and in general a non-PDF source is preferable.Thomas H. White (talk) 00:09, 28 January 2020 (UTC)
Can't we have both links? Constant314 (talk) 03:34, 28 January 2020 (UTC)
Good solution, put in both links—if you can persuade the cite template to do it. I've no idea how to do that; this is one of the many reasons I don't use them, too hard to get them to do something unusual. I don't agree that gbooks format is preferable to pdf. It is not possible to copy and paste passages from gbooks, which is highly inconvenient when one is trying to quote a passage. I understand the reason for deprecating sources that require a particular app, but there can't be many users who are unable to read pdfs and free apps that can open pdfs are widespread, not limited to just one vendor.
Gbooks visibility has to be location sensitive because the copyright rules are different in every country. Copyright law is a complete minefield. Google may be quick off the mark with releasing material that has gone out of copyright in the US, but the same is not true everywhere else. One can request Google to make a work available, but one has to do that individually for each work and for each country. Google does respond to these requests (I've made dozens of them myself) but it takes time and effort writing the case, there is a delay while they investigate, and results are not guaranteed. Sometimes Google cannot make a work available because they only had the snippets in the first place, not the full work, but you don't find that out until after you make the request. SpinningSpark 14:45, 28 January 2020 (UTC)
I don't know how you'd do that either, except by doing it as two separate refs to the same source. The problem with many technologies often come from things that were meant to be helpful. Many times an attempt to make things faster and easier both has the opposite effect and limits versatility. Google, for example, will modify a search based on many factors, including location and prior search history. I can google something at work, then go home and get an entirely different set of results from the same search. Google books is great, but can't beat the real thing. It changes all the time. Books available today may not be tomorrow, and visa versa. I've noticed this often occurs shortly after I've used one in an article, or they'll just change the pages available. (They're goal is to sell books after all.) Or sometimes I'll get a snippet view from using one search term, and a preview or even a full view from another. It's very erratic at times. I prefer PDFs whenever available. Zaereth (talk) 02:03, 29 January 2020 (UTC)
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