Talk:Passivity (engineering)

Merge

I had proposed merging passive component, active component, and active device several months ago. There were no objections (indeed, mostly apathy), so I just created an account and performed the merger. I have not copied any content from either of the active pages (both of which were classified as stubs, and had much less useful content than passive component). I have limited experience editing Wikipedia pages, so it may be helpful if someone more experienced can verify if I did this correctly. Also, during the merge, I removed "electrical" from 2 places, since passivity can be a property of non-electrical systems (indeed, it is commonly used in control system design for mechanical systems) -- the old active device page emphasized this. I probably should have made this two separate operations. Pmitros 00:59, 20 July 2007 (UTC)

Active and Passive

The old articles, Active component and Passive component may not have been entirely correct according to higher theory. However, they did explain the common circuit designer's usage of the terms. My understanding of this is that a passive component/circuit is one which does not contain a generator. A diode, under this thinking, is active, not because it is non-linear as it currently says in the article, but because its small-signal equivalent circuit contains a generator. This equivalent circuit may well be due to the non-linearity but it is not non-linearity per se that classifies it as active. The lists in the old articles of examples especially, made clear the division.

Another problem I have with this article is that active component and active device redirect to it but there should be a section in the article as a specific target for the link. It must be very confusing for anyone who types in "active component" to arrive here.

SpinningSpark 12:32, 4 October 2008 (UTC)

Nice article. A strange heading to find it under though. By the way, I personally define an active or passive component in my job of electronics and RF by, "If it has to have a power supply (a volatage applied to it) to make it work, it's active. If it doesn't need its own power supply, it's passive." —Preceding unsigned comment added by 138.162.8.58 (talk) 21:36, 31 December 2008 (UTC)

Both of your definitions are flawed, though SpinningSpark is certainly better than the unsigned one. Transistors alone are passive devices, and that's very clear when they work by dissipating heat. It's true that the transistor will often be used with an external supply of energy (e.g., a battery), but so long as the battery is included in the diagram, the transistor is passive. Circuit elements become active when you stop drawing the power supplies. For example, an operational amplifier without power rails shown is an active device, but an operational amplifier with its supply connections drawn in is passive. Finally getting back to the diode, if you're drawing a small signal model of a diode (e.g., a battery, resistor, and ideal diode in series), within that small signal model you might call the diode an active device. However, within that small signal model, it's the battery you introduced that is "active." In reality, it's the external battery driving the large signal model (responsible for the biasing) that's the active device. In the end, the diode is entirely passive. It's best to remember where the energy is coming from. The more you drill down, the more passive devices you find. —TedPavlic (talk/contrib/@) 13:27, 7 August 2009 (UTC)

The article currently says;

In some very informal settings, passivity may refer to the simplicity of the device, although this definition is now almost universally considered incorrect. Here, devices like diodes would be considered active.

This is sourced to The Penguin Dictionary of Electronics. Having now spent some time hunting down this book (two fruitless visits to libraries outside my area that are supposed to have it but don't, and finally buying a second-hand copy of the relevant edition) to my amazement the source says no such thing. The definition given is entirely compatible with diodes being active. There is nothing about this definition being informal, and nothing about it being widely considered incorrect. Considering that electronic catalogues commonly follow that categorisation and electronic text books use it, it is quite condescending to use this language. It is also rather aggravating given the flack I got for making uncited contributions in #Changes below. More to the point, it is a gross misuse of a source and introduces of uncited WP:POV. Even though I have been reverted in the past on this, I intend to rewrite this to something neutral and in line with the electronics sources (but perhaps without any mention of equivalent circuits - even though I still believe that is what underlies this classification). SpinningSpark 15:25, 17 August 2019 (UTC)

TeX is not so barbaric

Please don't write this:

$\int _{0}^{T}-<V(t),i(t)>\,dt$

TeX was invented by literate people (Donald Knuth) and you can write this:

$\int _{0}^{T}-\langle V(t),i(t)\rangle \,dt$

Michael Hardy (talk) 12:26, 7 August 2009 (UTC)

Yuck. You mean this:

$\int _{0}^{T}-\langle v(t),i(t)\rangle \,{\mathord {\operatorname {d} }}t$

—TedPavlic (talk/contrib/@) 13:20, 7 August 2009 (UTC)

Please explain this notation

This article says:

Given an n-port R with a state representation S, and initial state x, define available energy E_A as:

$E_{A}(x)=\sup _{x\rightarrow T>0}\int _{0}^{T}-\langle V(t),i(t)\rangle \,dt$

where the notation sup_x→T>0 indicates that the supremum is taken over all T > 0 and all admissible pairs {v(·), i(·)}.

The notation E_A(x) should refer to something that depends on the value of x (otherwise what's the x doing there?). The one place where x appears to the right of "=" is in "sup_x→T>0". The notation "sup_x→T>0" is not standard and accordingly an explanation of its meaning is given, but I don't see that the explanation succeeds. The expression following "sup_x→T>0" does not contain any occurrences of the variable x. Such an occurrence would not be strictly necessary if somehow the subscript "x→T>0" puts some constraint on T, so that the set of values of T involved somehow depends on x. But the subscript doesn't do that. The notation "x→" always makes x a bound variable in any of its uses I've ever seen, and I don't see what it would mean otherwise. If the whole thing is to depend on x as seemingly required by the notation "E_A(x)", then x needs to appear as a free variable.

When you write

$\lim _{x\to {\text{something}}}\left({\text{something}}\right)={\text{something}},\,$

then the "something" at the end—the bottom-line answer—does not depend on the value of x. Likewise when you write

${\text{something}}\to {\text{something as }}x\to {\text{something}},\,$

then the second "something", which is the limit that is approached—the bottom-line answer, does not depend on the value of x.

As written, it's clumsy and opaque. Michael Hardy (talk) 12:38, 7 August 2009 (UTC)

The editor who inserted the original definition was clumsy and forgot to properly define that notation. I've gone ahead and defined it as best I can without rewriting the whole section of the paper it's from. Basically, the x is an initial state that generates voltage v and current i trajectories. The integral calculates the power of those trajectories up to time T. The supremum gives a bound on that energy over all time T. So it's a little like...

$\sup _{T(x)\to \infty }$

but that notation makes you think of the $\limsup$, which would be incorrect. It's just meant to be an upper bound on a set of powers. Each initial state x has a different set of powers, and each set has a different upper bound. All upper bounds must be finite for the system to be passive. —TedPavlic (talk/contrib/@) 13:35, 7 August 2009 (UTC)

Thank you. It's comprehensible now. And I'd actually missed the infelicitous switch from capital V to lower-case v. Michael Hardy (talk) 16:10, 7 August 2009 (UTC)

Changes

I removed two factually inaccurate statements:

To be fair to this view of passivity, a non-linear device will inevitably include a generator in its small-signal equivalent circuit and so will be modelled as a source of energy. This arises because a linear approximation to a small section of the transfer function is unlikely to pass through the origin and such an offset requires a generator in the equivalent circuit to produce the value of the offset current or voltage. For instance, a forward biased diode can be modelled as a resistor in series with a DC offset as far as small signals are concerned.

This is incorrect. A diode small-signal model (for a normal diode) is just a resistor of the slope of the IV curve at the point of linearization (coincidentally, if you look closely enough, most resistors include some amount of non-linearity as well). The definition proposed by SpinningSpark is non-nonsensical (this is just the tip of the iceberg as to how badly nonsensical).

Sorry for breaking up your post but you have made two completely separate deletions here which need to be addressed separately. For a diode where the signal remains within the substantially linear portion of the slope, the transfer function is precisely identical to a d.c. generator plus a resistor. In many applications, the d.c. can be ignored because there is no d.c. component to the signal and is going to be subsequently removed with a coupling capacitor or some such. This does not invalidate the model, it just means that the full model is not needed for that application. The paragraph is not at all a proposed definition, it is merely commenting on the definition in the paragraph above it (which currently remains in the article). SpinningSpark 15:03, 9 October 2010 (UTC)

You do not understand the definition of small signal model. Please see a copy of Gray and Meyer, or any other introductory text on analog design for a definition of small signal model. You have one valid point -- the article is not very readable to beginners. To some extent, this is necessary, since it is a complex topic (largely because it is used in many engineering disciplines -- from analog design to airplane controls -- and has to be explained to readers coming from multiple fields), but also because the writing in the article could use improvement. What you are doing, however, is not cleaning up the article. You are adding statements that range from imprecise to incorrect, and they will at best confuse a beginner. I do not believe you have the knowledge or understanding to improve this article -- you very obviously do not understand the material yourself, and so are incapable of explaining it further. I do not have the time or energy to either try to educate you, or to get into revert wars with you. You are also violating the rules of Wikipedia by posting uncited "original research." Wikipedia is not the place for novel (and incorrect) explanations or rationalizations. Of course, if you really feel like vandalizing Wikipedia, that is your prerogative. 24.128.191.214 (talk) 23:18, 13 February 2011 (UTC)

but the desired signal is invariably attenuated. If no resistors are used, the amount of signal loss is directly related to the quality (and the price) of the components used.

Both active and passive filters will include gain errors due to imperfect components. In passive filters, these will typically show up as attenuation. In active filters, these may show up as attenuation or gain, but attenuation is also more common. There isn't a fundamental difference here. There are also corner cases (e.g. superconductors) where there is no attenuation. This is misleading in the typical case, and incorrect in the corner case. —Preceding unsigned comment added by 24.128.191.214 (talk) 08:20, 9 October 2010 (UTC)

I agree that this is badly worded and the quality/price thing is at least irrelevant and possibly wrong. However, there is a valid point buried in here, the fundamental difference with an active filter is that losses can be compensated with a gain adjustment which is impossible for a passive filter. SpinningSpark 15:08, 9 October 2010 (UTC)

When you figure out your buried point, feel free to repost it, with a proper citation. For now, you are posting incorrect, uncited nonsense. Transfer function is described in terms of voltage gain (or, in rare cases, current gain), not power gain. Passive circuits can have voltage gain, or current gain. They just cannot have power gain. It is perfectly straightforward to compensate for voltage attenuation in a passive filter with voltage gain. In most cases, this is a bad idea for both passive and active filters, since it increases sensitivity to component variations, but there are cases where it makes sense. 24.128.191.214 (talk) 23:18, 13 February 2011 (UTC)

Classic diode and transistor models are misleading

To present a non-linear resistor having an orthogonal IV curve as a source (the classic wide-spread approach) is a completely misleading concept. Typical examples of this misconception are the forward-biased diode presented as a voltage source and the collector-emitter junction of a transistor driven with constant base voltage presented as a current source. They are not sources at all; they only resemble sources in certain parts of their IV curves, and sources acting only as loads at that. A diode resembles a voltage source driven by a current source and a transistor resembles a current source driven by a voltage source. In this role, the diode keeps constant voltage drop across itself while the voltage source keeps constant voltage (the two are different). These elements are passive resistors - only not "static" (ohmic) but dynamic (differential) resistors.

Diodes and transistors are modelled by voltage and current sources because they consider there are not generic elements with such characteristics. Actually there are such generic elements but they are forgotten. These elements are (or can be) named respectively "voltage-stable resistors" and "current-stable resistors" (IMO "voltage-stabilizing" and "current-stabilizing" would be better). So, a diode (ordinary, zener, LED, varistor, etc.) is a passive voltage-stable nonlinear resistor and a transistor (PPTC, etc.) is a passive current-stable nonlinear resistor

The sentence "...a non-linear device will inevitably include a generator in its small-signal equivalent circuit..." (especially this "inevitably") is misleading. The next sentences - "...so will be modelled as a source of energy..." and "...such an offset requires a generator in the equivalent circuit to produce the value of the offset current or voltage...", strengthen this misconception. Of course, "...a forward biased diode can be modelled as a resistor in series with a DC offset..." but there is no need to do it if there is a generic voltage-stable element. Circuit dreamer (talk, contribs, email) 18:58, 16 November 2010 (UTC)

Passive and active adapters in computing and audio

In computing, audio, and some other fields where similar-but-different things are often connected to each other, it is useful to make a distinction between passive and active adapters. Passive adapters are usually simple connector and pinout adapters, while active ones usually contain logic circuits and/or one or more analog gain stages. For example...

• For example, older "USB and PS/2 compatible" mice usually were equipped with a USB connector, but came with a passive adapter—a pinout adapter with no logic in it. The device's onboard firmware could determine whether it was connected to a USB or PS/2 port and so would "speak" the appropriate protocol on the appropriate pins. Whereas older PS/2 peripherals require an "active" adapter (one that includes logic so that it looks like a USB HID to a host computer) to connect to a USB port.

• The ubiquitous connector that allows connecting a VGA monitor to a DVI-I port on a graphics card is a passive adapter (i.e. only a pair of connectors with wires in between).

• In audio work there are passive mixers and active mixers, the former including only pots and resistors, the latter including gain stages.

• In audio work one can also find both passive and active converters between balanced and unbalanced lines. (A passive bal/unbal converter is generally just a transformer along with, of course, the requisite connectors.)

These applications seem to me to be in the realm of this article but are not explicitly described here. I feel they should be. Comments? Jeh (talk) 10:08, 31 January 2013 (UTC)

Vandalism / edit wars

This article keeps being either ignorantly edited, vandalized, or brought to edit wars by an ignorant user.

The reason this topic is complex is because the terms "passive" and "active" are often used pretty colloquially ("I don't know what it is, but I know it when I see it"). People bump into some random definition on some random web page or book, but when you get down to it, all those definitions are different and often in conflict with each other. The electronic engineering community converged on proper, rigorous, formal definitions but (1) these definitions are (necessarily) somewhat complex, (2) many people (especially amateur circuit hackers) don't know them, and (3) a range of colloquial uses is common (especially in books by amateurs for amateurs, but also often in electronics catalogs. Spinningspark: if you really want a range of conflicting references, pick up a vendor catalog; you'll find marketing departments use these terms every which way possible). The point is you can find **some** sources defining 'active' and 'passive' any which way. Occasionally, random users come up on this page and edit it, based on what they learned in some random place. There's one particular aggressive, ignorant Wikipedia user who insists on making changes which are usually simply incorrect (and it's striking -- literally every sentence can have an error -- I'll walk through the current edit below).

While that's no reason to perpetuate ignorance, there are people with far more energy to get into these things than myself. I'm not sure what the right course of action is, or whether Wikipedia has procedures for managing this.

The current version starts:

"In electronic engineering, devices that exhibit gain or a rectifying function (such as diodes) are considered active."

This is false. All of the definitions come from the electronic engineering community. The difference is that this is an informal usage, while the above versions are formal definitions.

The next chunk completely confuses the term solid-state. This is evidenced in the edit history: "That's just nonsense. Capacitors and resistors are generally solid state." Solid-state has a mixture of definitions, but in the context of circuit design, generally this term refers to semiconductor devices. See the wikipedia entry for solid state which starts: "Solid-state electronics means semiconductor electronics; electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs)." In this context, an electrolytic capacitor, discrete resistor, or similar would **not** be considered solid-state. There is a gray zone for resistors and capacitors on an IC (which are semiconductor-based, but don't make use of the properties of the substrate as a semiconductor), but the overall IC, as a silicon device, is still considered solid-state. Of course, at a systems level, the definition changes (for example, if you're plugging an SSD into a computer, that means "no moving parts," and it may contain non-semiconductor devices).

Next, we see this gem:

"Only capacitors, inductors, and resistors are considered passive.[3][4]" -- It's worth pointing out what the sources for this (incorrect) definition are:

1) "The New Penguin Dictionary of Electronics," I couldn't find on-line for the 2nd edition. The third edition is a text from 1998 whose author also wrote dictionaries of astronomy, computer science, physics, computing, etc. That stands against standard academic texts on the topic. This book hasn't even been bothered to be digitized by Google Books or Amazon Look Inside, so it's impossible to tell what it even says. 2) A one-liner in "Crash Course in Electronics Technology." Really. Looks this up in Google Books. By Google's search, this book mentions 'active' a total of seven times in the whole book. The definition of 'passive' contradicts itself: it states that they do not modify signals (an RC filter doesn't modify a signal?), and later defines all filters as passive (a Sallen-Key is passive?). I don't really fault this book, since this isn't a focus of the book, but I do fault the editor for citing what's clearly a non-reference.

This stands against standard texts used at first-tier universities for teaching electronic engineers. What's frustrating is the article already has canonical citations from people who are generally considered the world's experts in this field (faculty at MIT, Berkeley, etc.).

Continuing, we get this incorrect statement:

"In terms of abstract theory, diodes can be considered non-linear resistors, but non-linearity in a resistor would not normally be directional, which is the property that leads to diodes being classified as active."

Yes, plenty of perfectly passive nonlinearities are directional and can rectify. See an electrolytic capacitor, for example, or even a slightly corroded connector (which acts a bit like a Schottky diode). If you define those as active, you run into all sorts of contradictions.

Finally, we get into this:

"United States Patent and Trademark Office is amongst the organisations classing diodes as active devices."

That's a USPTO classification, not a definition. It's used for routing patents to the right examiner. It's not even a classification of "active device;" the class is: "ACTIVE SOLID-STATE DEVICES." The key words here are "solid-state." Which is a term our editor doesn't seem to understand either.

I'm sure that in response to this comment, we'll get another edit by this user, perhaps with surface changes to the above, and get another incorrect page. I'm not really sure where to go from here. As it is, we had a section of an article edited where now quite literally every sentence contains a technical error, and quite often multiple. On some level, Wikipedia shouldn't have incorrect pages. The right course of action would be to revert to the last correct version, and then have editors who understand the subject matter work to simplify this page. On some other level, it's clear someone has way more time on their hand than anyone else here, and at this point, I'm willing to just let them take over, and let Wikipedia perpetuate ignorance and have one incorrect page. — Preceding unsigned comment added by 73.17.150.215 (talk) 12:12, 4 January 2020 (UTC)

I've moved this thread to the bottom of the page because that is the convention here. Please don't call people vandals who are making good faith contributions. Especially don't put it in the section heading. I don't much care for being called ignorant either. I worked in electronics for more than forty years before I retired. Let's just stick to the issues shall we?

The Penguin Dictionary of Electronics was not added as a source by me, nor would it be my first choice of a source, but I went to the trouble of prurchasing a copy to see what it actually said, which led to my edits. It turned out to completely contradict the text it was claimed to be verifying. See my comments in #Active and Passive above. I fully understand the formal definition of passive, but it's not Wikipedia's place to tell people who use some other terminology they are wrong. We need to quote a source on that. SpinningSpark 19:48, 4 January 2020 (UTC)

It's like an anti-vaxxer actively maintaining the Wikipedia page on vaccines. It's in good faith. It's someone who studied the topic in-depth, at least in a sense. The issue is the article has serious technical errors, and there's no way to keep it correct, since there's a very excited, active editor who insists on introducing them. See also Dunning-Kruger effect. The whole second part of 'Incremental passivity' has nothing to do with 'incremental passivity' as of this post. Much of the section on passive filters is wrong too (more linear? linear expensive? Not in 2020, or even 2010). No one on the Internet can hope to keep up with your edits, though. So keep at it. Introduce things you feel in your gut are right, and confuse new engineering students who hope to use Wikipedia to learn something correct. 73.17.150.215 (talk) 20:01, 28 April 2020 (UTC)

I couldn't help but notice the page, and Wikipedia as a whole have only about 3 paragraphs in total on passive filters. This makes me wonder if the inept amount of information on such a diverse topic could be down to you guys having to remove large portions that were edited in this manner.

Though, that doesn't explain the lack of a dedicated page. I'm just speculating. I already made a talk page on it, but it confounds me that the whole of Wikipedia only has 3 paragraphs on passive filters. It's baffling to the point of being fascinating. I'm more curious how/why it happened at this point and when I saw this page, it got me wondering. But I think there's more to it than one overzealous contributor. VoidHalo (talk) 22:11, 24 September 2023 (UTC)

No dedicated page for passive filters? Very little information. Search leads here.

The information on passive filters in this article, and Wikipedia as a whole seems woefully inept. Unless I'm missing something.

There are only about 3 paragraphs worth of information, and as far as I can tell, there is no dedicated page for the topic. Searching for (passive filter) minus the parentheses redirects to the section on the subject in this article.

I find it difficult to believe that the whole of Wikipedia only has 3 paragpraphs about passive filters on it. I'm sure I recall reading a dedicated article at one point. But I can't seem to find any such article.

Considering entire textbooks have been written on the topic, and the wide range of topologies, analysis, mathematical models, and so much more that don't even scratch the surface, it makes little sense that the whole of Wikipedia to only have 3 paragraphs on the topic.

There is a page about active filters that's rich with information, and very well written. So, it makes no sense to have little or nothing about passive filters. That's the depth of coverage I was expecting for passive filters, as well.

I feel like I must be missing something. There HAS to be a page on passive filters. Whether it's just not as intuitive to navigate to the page or the page is called something else, I don't know. But I refuse to believe one doesn't exist and this is all there is.

sorry this went on a bit long. I hope readers can appreciate where I'm coming from. VoidHalo (talk) 08:07, 22 September 2023 (UTC)