Best Capacitor

[dr.power]

Hi there.

What i the best non polar capacitor for the frequencies below 100KHz?
Specially for generating an audio 90 degrees of phase difference use for an SSB modulator?

I myself am thinking on the ceramic and polyester caps. What is your idea?

Thanks

 

[dknguyen]

Ceramic should be fine. It's the cheapest and most common of them too. Polyster is starting to get fancy.

 

[audioguru]

Ceramic capacitors have wide tolerance and change value with temperature and voltage changes. Not good.
Metalized plastic film capacitors are available everywhere with 5% tolerance and do not change value. Very good. They do not cost much.
I used "polyester" capacitors 45 years ago and they were different from today's metalized plastic film ones.

 

[crutschow]

For best capacitance stability use a film capacitor with a stable film material such as polycarbonate.

 

[MrAl]

Hi,

Check out Silver Mica capacitors.

 

[audioguru]

I have never used and never seen polycarbonate or silver mica capacitors. I use European metalized plastic film capacitors for audio coupling and timers. They look like this that have their leads spaced at 5mm (0.2"):

 

[Nigel Goodwin]

I have never used and never seen polycarbonate or silver mica capacitors.

How come you've never seen Silver Mica capacitors?, they are very high quality capacitors frequently used in oscillator and RF circuits.

They have good tolerences and excellent stability.

 

[dr.power]

Ceramic capacitors have wide tolerance and change value with temperature and voltage changes. Not good.
Metalized plastic film capacitors are available everywhere with 5% tolerance and do not change value. Very good. They do not cost much.
I used "polyester" capacitors 45 years ago and they were different from today's metalized plastic film ones.

Thanks audioguru for all your helps.

Actually There are several kinds of capacitor here in my place. Indeed I know the ceramic/Mica/ electrolyte/Polyester caps by their shape. There are another kinds of caps the electronic store holder calls them as "plastic" caps which are used in TV's and are suitable for higher voltage/frequency application (actually they seem to be MKP/FKP caps, I have used them in a royer oscillators ). I want to say I have no clue what are "metalized plastic film" capacitors. I mean I have no idea How to detect and realize metalized plastic film caps? Are they good enough for oscillator circuits? I want to make an Oscillator out of a 4047 IC but I have a badly consideration regarding the capacitor used in its RC section (changing the value by temperature and the voltage and so on)

 

[dr.power]

For best capacitance stability use a film capacitor with a stable film material such as polycarbonate.

Thanks but how to detect that?

 

[dr.power]

Hi,

Check out Silver Mica capacitors.

Thanks, I know MICA caps. But do not now if they are Silver or not. How to know that?
The Mica caps I ever use mostly are green colored (Although the below page shows them as polyester ones!):
https://images.search.yahoo.com/ima...b=13gt3mlqs&sigi=122ctoenb&.crumb=1lTWEulRN.6

 

[dr.power]

How come you've never seen Silver Mica capacitors?, they are very high quality capacitors frequently used in oscillator and RF circuits.

They have good tolerences and excellent stability.

Are they good for frequencies lower than 10KHz too?
Why they are called "Silver"

 

[audioguru]

Oriental metalized polyester film capacitors are usually green and are shaped like a chewing gum tablet. They use a code for their value and tolerance (104J).
European or American ones have the box shape (look in Google Images). They show the true numbers (100nF, 5%).

 

[RCinFLA]

It is hard to tag a 'best' capacitor. There is a best capacitor for a particular job. Some apps need good temp stability, some need low ESR, some need low leakage, some need low parasitics inductance, some need low dielectric absorption.

Mica is pretty stable, low ESR capacitance but has relatively high parasitic inductance compared to ceramic. Don't see Mica too often these day due to high cost. Ceramic dielectric does not give up all its charge (dielectric absorption) so you don't want it for a frequency synthesizer loop filter. High K dielectric ceramics have low Rs and high capacitance for unit volume but capacitance can be a function of applied average bias.

 

[dr.power]

I found a kind of caps in my place called as "MKT" capacitors.
I do not have any info about their performance temp stability and accuracy. Any idea plz? Are they good enought to be used as audio phase shifters? I need 47n, 33n and 6.8n for my speech phase shifting filter.
Furthermore, Are these MKT caps kind of metalized (polyester) film capacitors you are talking about?
Here's the image for MKT caps

 

[dr.power]

BY the way I found mylar capacitors & multi layer caps here in my place. Plz any suggestion for them used as a 90 degree speech shifter filter?

Thanks

 

[dr.power]

By the way, Here's the speech phase shifter which I am talking about.

 

[audioguru]

Your filter attachment does not work.
The MKT capacitors you showed are a very stable metallized plastic film type. Use a tolerance of 2% or 5%.
"Multi-layer" capacitors are ceramic and are not stable. They are good as a power supply high frequency filter.

 

[dr.power]

Thanks audioguru for your inputs,

Your filter attachment does not work.

What do you really mean By that??!! just open it in a new window and it does work...

The MKT capacitors you showed are a very stable metallized plastic film type. Use a tolerance of 2% or 5%.

So I can use them for the such a speech filter right? Are you thinking that using MKT caps is the best choice or at least good enough choice for the said filter, or there is another better kind type cap for that job??
By the way though a tolerance of 2 to 5& is good enough but can I find those caps with a tolerance of say 1% or even lower so that enshure the said filter from any miss phase??

"Multi-layer" capacitors are ceramic and are not stable. They are good as a power supply high frequency filter.

Oh I did not realize that, Thanks for reminding that.

 

[audioguru]

Your attachment "is not available" (in its properties) and therefore it does not open.
It is supposed to be a thumbnail that gets larger when clicked on.

 

[dr.power]

Your attachment "is not available" (in its properties) and therefore it does not open.
It is supposed to be a thumbnail that gets larger when clicked on.

It is strange,
I tried it fir several times, And every time I could see it by clicking on it. Any way here's it is in zip format.