Extreme 220GHz+Broadband Silicon Capacitor X2SC 0201M 22nF BV11

All silicon capacitors are relatively expensive, they're specialty parts that generally go into expensive things (mmWave airport scanners, optical backhaul, etc).

The temperature stability looks fantastic, but it has a voltage coefficient for capacitance which is worse than film caps.

From datasheet:

> Voltage <-0.1%/Volt

That is significant: over just a 10V swing, it could be as high as 1%.

For a plain old polyester film cap, this is something like ±0.0001%/Volt, IIRC.

If you have an audio signal swinging over a -12 to +12 V range being coupled through a thing like this, there will be measurable distortion arising from ~ 0.1%/V variations in capacitance.

Not that you would want to necessarily do that in the first place, since this thing has an 11V breakdown voltage, nothing to write Mom home about.

There is no one-cap-fits-all; right cap type for the right job.

Consider the device that they gonna be placed in, it's basically nothing.

Same here. That's made my week.

It may seem overly simplistic, but 2-port models for capacitors can be configured in series (as shown here) or in shunt (much more common for power distribution network applications). So, as basic as you might think this diagram is, it is entirely expected to be there so that we instantly know if the S-parameters are in series or shunt configuration - it would be more unusual if it were missing.

Hey, at least we know it's not polarized. Knowing's half the battle.

I never understood why nF is less frequently used than uF or pF. To me, the logical thing is to express the capacity in units that are between 1 and 1000, like it's done with resistors and inductors.

nF is used a fair bit in audio circuits. Nanofarad-range capacitors, typically from 1 to 100 nF, often appear in filtering circuits. From time to time, values down to around 300 to 500 pF may appear. Anything around 100 pF or less is typically for dealing with unwanted high frequencies in some way. On the other end of the scale, microfarad-range caps in the signal path appear as couplers into low-ish impedances, where good bass response is required. For doing things" with the signal, other than passing it through with bass intact and filtering out RF, the workhorses tend to be caps that are nicely measured in nanos.

In terms of brevity on a schematic, it about breaks even for two-digit nF values and wider as in 22n vs .022, and only when we have a blanket rule that when units multipliers are omitted from capacitors, they are understood to be μ. 2n is shorter than .002; and harder .0047 is easier to misread as .047 compared to 4.7n.

NOTE: You will may across audio schematics which do not write the "n"! It is assumed that any capacitance which is an integer like 33, or a real number >= 1 like 2.7, is nanofarads! Together with the convention that fractional capacitances are implicitly microfarads, so that 0.47 is microfarads.

In my local brick-and-mortar electronics shop, packages of capacitors 1nF and higher tend to be labeled in nF if they are film caps or ceramics. Electrolytics use μF; a bag of 0.1μF electrolytics would be labelled that, and not 100 nF, but the same-valued film cap will probably be 100 nF.

No, not if you want 22 nF. That's a pretty substantial capacitance. It would need to be quite big on a PCB. That would mean significant inductance, and thus, bad performance at high frequencies.

Certainly not at these frequencies and corresponding high capacitance values; getting 22nF out of a PCB even with ECM would require quite a large surface area and at 220GHz you can't have that since your wavelength is so short; you'd just be making a giant resonator instead.

Not if it is to be 22 nF.

To make a 22 nF capacitor using a pair of copper pours separated by a 1.6 mm thick old school two-layer PCB, we would need something like 10 square feet! It would have to be an electronics art project, intended to be displayed on a gallery wall. :)

That goes down to something like 90 square inches if the separation is a 0.1mm thick layer of a thin four-layer PCB: still an impractically huge area.

Capacitors achieve their density in a small package by two tricks: extremely tiny dielectric gaps, and convoluted surface areas.

For instance, electrolytic caps achieve a big surface area due to using rough, anodized aluminum (or tantalum) for the anode (mnemonic: anodized aluminum -> anode). Then every ridge and crevice in that anode is available for capacitance due to using an electrolytic gel for the cathode. The roughness of the anode and the gel optimize for high surface area. Then the thinness of the oxide layer optimizes for a small gap size, also favoring high capacitance.

Has been done for decades. Buried capacitance materials like FaradFlex MC12TM exist and are really good, but are not too often used.