7

Based on a description I read here.

Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material.

I was thinking Caps are usually built of "layers" of "stuff" (paper, plastic, glass, mica), but they can also have fluid in them (electrolytic), which is not solid. The article I was reading mentioned that vacuum tubes aren't solid state because they contain/use gas, so would that be the same for a capacitor? or are they generally considered solid state devices anyway?

placeholder
  • 29,982
  • 10
  • 63
  • 110
Mike
  • 503
  • 1
  • 3
  • 11
  • Mike, could you give more context for your question? For what purpose do you need to _strictly_ sort devices into solid state and not? Did somebody give you a requirement to "use only solid state components"? If so, what's the underlying reason for such requirement? – Nick Alexeev Oct 26 '12 at 18:14
  • @NickAlexeev - I should add to every post I make that I may have no idea what I'm talking about. (software guy) :) This is just for my understanding of electronics in general. If parts can't be sorted into "solid state" or not strictly, that's a good answer too. I wasn't aware of that. – Mike Oct 26 '12 at 18:22
  • This is a pointless question. Why does it matter whether a capacitor is considered "solid state", whatever that means exactly? You use capacitors according to their properties, not because someone claims one to be solid state or not. Actually some types of caps could be reasonably considered solid state and others really not. But again, so what? – Olin Lathrop Oct 26 '12 at 20:28
  • @OlinLathrop - So you think the term "solid state" is meaningless? – Mike Oct 26 '12 at 20:50
  • 1
    @Mike: Yes, as applied to capacitors. Again, what does whether a capacitor is "solid state" or not tell you so that you will do something differently? Capacitors have various parameters you have to know anyway to chose the right one. Once you have those, whatever might mean it is solid state or not will be included. There is no exact definition of "solid state" in this context. It's not exactly a marketing term, but sortof. – Olin Lathrop Oct 26 '12 at 22:10
  • @OlinLathrop - We, It's educational. Again, I'm not trying to "do" anything. I was looking up memory types, it was mentioning solid state flash, didn't know what "solid state" really meant so I looked it up and found the wikipedia mentioned in the post. From there it sounded like solid state had to do with a device being "solid"... thinking about electrolytic caps was wondering if that was correct or not. So... long story, but that's why this is important, not for use per say, but just to understand the concept. – Mike Oct 26 '12 at 23:04

4 Answers4

10

For the 1st half or so of the 20th century, vacuum tubes (or "valves") were used for rectification (diodes), amplification (triodes, tetrodes, pentodes, etc.), and, for most of the 20th century, displays (CRTs).

In these devices, a space current of electrons exists between the cathode and anode, i.e., the charge carriers are transported through a vacuum*.

In the 2nd half of the 20th century, semiconductor technology advanced and rapidly rendered vacuum technology obsolete (except for CRTs). In semiconductors, the charge carriers are transported through the crystal lattice of the solid semiconductor, thus the term "solid-state" to distinguish these types of devices from the vacuum devices.

Generally, this is the context in which "solid-state" is used and understood.

In the case of capacitors, the dielectric doesn't support charge transport, i.e., there isn't a flow of charge carriers through the dielectric in a properly functioning capacitor so the dielectric falls out of the scope of the definition you've quoted.

*with some exceptions.

Alfred Centauri
  • 26,502
  • 1
  • 25
  • 63
  • 1
    Informative, but doesn't quite answer the question - does the electrolyte count as "vacuum" (non-solid) or "solid", despite being liquid? – exscape Oct 26 '12 at 18:42
  • 2
    @exscape, there is no charge carrier transport through the dielectric of a capacitor whether it is solid or not. Also, I thought I did answer the question: the term "solid-state" is generally understood in the context of active devices such as vacuum tubes and transistors rather than passive devices such as resistors and capacitors. – Alfred Centauri Oct 26 '12 at 18:49
  • 1
    Actually @exscape 's comment is what I was thinking to, but your clarification here in the comments helped. I didn't catch the "active" vs. "passive" thing on the first pass. Thanks! – Mike Oct 26 '12 at 18:55
9

"Solid state" is just a marketing term which means "the amplifying, switching and rectifying components are semiconductors and not vacuum tubes or relays."

A transistor radio containing an alkaline battery is still "solid state".

Note that a "solid state relay" is not an alternative to anything in which electrons move through liquid, gas or vacuum. In a mechanical relay, electricity moves through copper!

So "solid state" essentially means something like "semiconductor-based alternative to old-fashioned Rube Goldberg contraptions that require boiling electrons off a heated cathode, or place moving parts into the circuit". In this sense, solid is perhaps no so much reference to a phase of matter, as a hint about the durability and reliability.

The origin may be "solid state physics", but the average consumer doesn't know that, and the term is applied to an entire device ("solid state audio amplifier"), which includes components that are not the result of solid state physics (such as wires, resistors, inductors, capacitors, ...).

Kaz
  • 19,838
  • 1
  • 39
  • 82
2

Solid state devices are defined by the conduction properties with the physical layer being motion of electrons and holes carrying current. Although diodes and caps are both considered passive devices, Capacitors are defined by the delectric insulating properties as the primary function. They may be used to store energy, block DC, resonate with inductive parts whereas the leakage and series conductance are non-ideal properties.

Polarized capacitors may have zener diode like leakage, but their primary purpose is the dielectric properties (phase shift, time delay) rather than the conductance properties of leakage current or series losses or motional noise.

Devices which are not solid-state devices include vacuum tubes (thermionic emission) PTC,ICL (poly-phased conductors), tungsten filaments, (thermonic IR emitters which also give visible light), and of course Capacitors, and "batteries not included" as well ;)

Devices which are considered Solid State include Liquid Crystal Displays (LCD) due to non-linear controlled polarization states of the crystal structure within the liquid, and of course LED's and OLED's.

The begining of "Solid State" Physics was Xray diffraction in crystalography in 1912 and SS devices were initially developed by Schlockey et al in 1948. The crystalography properties for electronics are what defines "Solid State devices", even though LCD's have a liquid medium, the crystal lattice atomic properties are what defines this field in Physics and Solid State devices.

Tony Stewart EE75
  • 1
  • 3
  • 54
  • 182
1

Now to complicate the issue ... How about solid state capacitors? i.e. ones that are made in a semiconductor process of Oxide growth and deposition and patterning? Thats really the answer there isn't? Solid state is a description of manufacturing not necessarily of what the device is or dones. So a capacitor is both a solid state and a non solid state device.

But solid state in the early years of consumer electronics actually was used to describe how components where joined together with the first "solid state" TV's using what we today would call PCB's or PCA's or PWB's. Prior to the PCB revolution component leads were soldered together and perhaps even wirewrapped in production. So another use of the term.

Solid state devices arose from solid state physics and so that use is appropriate.

placeholder
  • 29,982
  • 10
  • 63
  • 110