The pros and cons of various capacitor types

[JPBEngr]

Hello,

I know that capacitors are made from several different materials, but when I don't really have a good grasp of are the advantages and disadvantages of the different materials. For instance, I have built a few simple power supplies and used electrolytic caps (because I wanted a large amount of capacitance). I also made an RF resonator and used a ceramic disc capacitor (I didn't need much capacitance.) There are many more types of capacitors being made, Mylar, mica, tantalum, etc. My questions are as follows:

1. Is there a gold standard capacitor? When in doubt always used X type?
2. Is cost vs. capacitance a factor?
3. How about capacitor volume (package size) vs. capacitance?
4. How about frequency ranges? I'm pretty sure that electrolytics aren't good for high frequency applications.
5. Which type has the best/worst ESR? I could look this one up.
6. Dissipation factor is a term I have read about, but I don't know the meaning. Is there a preference here?
7. Is the parasitic inductance better or worse in one particular type, or is this more related to construction method?

I realize some of these questions may be a bit naive. My degree is in Mechanical Engineering not EE. I suspect there is some strong opinions on this topic (probably in the high end audio world). I would like to make some sense of it. Thanks.

John

 

[geekEE]

This may help:

http://www.radio-electronics.com/info/data/capacitor/capacitor_types.php

There's no ideal capacitor. Everything is a tradeoff in terms of size, cost, tolerance, ESR, voltage-rating, etc.

Glenn

 

[MacGyverS2000]

There's a major difference between opinion and fact.

Fact: Construction method has a major impact on ESL/ESR.
Opinion: Caps made with gold affect the "sweetness" of the audio.

Stick with fact. There is no gold standard for caps, it is always a toss-up between choosing one that meets/exceeds the required specs while remaining under budget. For example, an MLCC is going to have lower ESL than a wound type, but you may not get the capacitance level you need in an MLCC without spending a fat wad of cash.

The easiest way to determine what caps are best would be to look at commercial products and what they use (audiophile-level equipment is removed from this group). You can bet the companies involved in the manufacture have already done a decent job at comparing cost to performance... if it looks like you may be on the edge of performance, read the specs yourself for a specific cap type and make a determination on it's suitableness.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

Your question is similar to, "Which is the best metal?" Every metal and metal alloy is suitable for a certain range of requirements and applications.

Likewise, asking which capacitor is the "best" has no answer. Every capacitor type that's manufactured has one or more specific applications for which it's the "best." There is NO capacitor that can do everything, so there cannot be a "best" capacitor overall.

Until you define a specific set of requirements for your design, you cannot even begin to choose a capacitor. You would not use only titanium for every design, why would you expect to use just one type of capacitor?

TTFN

FAQ731-376

 

[Noway2]

There is another important aspect with regards to capacitors and their application. Every capacitor has capacitive and inductive properties, which are naturally frequency dependant. The exact properties of the capacitor depend on things like type, size, package, value, etc. This feature can be extremely important in certain applications, such as what type and value to use for decoupling ICs.

 

[OperaHouse]

Tough question. I noticed that capacitor manufacturer's spec sheets seem to be more vague than they used to be. Without a geed capacitance meter you are left in the dark. sencore.com has some good application notes that tell some of the story. I can't even gt capacitance meters to agree that use different evaluation methods. One thing to remember is polyester makes cheap suits and cheaper capacitors.

 

[JPBEngr]

As a mechanical analogy, I guess in some ways this is asking what is the best type of screw or bolt. There are several materials, threads, drives, heads, etc. Titanium would be good in a application for light weight and/or high temperature. Stainless steel would be good for corrosion resistance (depending on the type of stainless steel). Grade 8 bolts have good strength and are relatively inexpensive. Aluminum may be a bad application for vibrations since its fatigue strength goes to zero as it the number of stress cycles increases. Fiberglass and nylon screws/bolts are for electrical insulation, but their strength and heat resistance is low. Coarse threads are typically preferred to fine threads for assembly since they are more difficult to cross thread, but the cross-sectional area (and strength) is slightly reduced. And so on...

1. From a audio or psycho-acoustic consideration does one type of capacitor sound better than any other? Paper caps? Electrolytic? Ceramic? Polypropylene?

2. What is a typical upper frequency limit for an elctrolytic capacitor?

3. Is the big advantage to a tantalum capacitor the volume vs. capacitance?

Thanks for you fast responses.
John

 

[geekEE]

John,

1. Yes, but there is an enormous amount of touchy-feely info out there that talks about "warm bass" or "crisp, but not overpowering highs". Here's an article by the well-respected Walter Jung that actually takes a more scientific approach to quantifying capacitor non-linearity (

http://www.reliablecapacitors.com/pickcap.htm).

There's still no "best" capacitor because it will depend on things like what value range you need. However, I would say that the amount of distortion introduced by capacitors usually pales by comparison to the distortion introduced by speakers, so you probably don't have to worry too much.

2. From what I recall the inductance increases as the electrolytic value goes up, so the max frequency goes down. However, I don't know the specific frequencies.

3. Yes, the size is a big advantage. Another advantage is that tantalums don't dry out and change characteristics over long periods of time like electrolytics.

Hope this helps.
Glenn