Maker Pro
Maker Pro

which capacitor is best

grahamdavidmoore

Jun 23, 2014
9
Joined
Jun 23, 2014
Messages
9
hi, I've just built a circuit from the internet which calls for a "C0G/NP0 or a mica for better stability", I have some polystyrene and some polycarbonate and some metalised film, which ones would be better? many thanks.
 

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
Messages
5,178
Can you post a circuit diagram and point to where the capacitors are on it. Gives up a better idea and we can then answer you accurately.
Thanks
Adam
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,700
Joined
Nov 17, 2011
Messages
13,700
Polystyrene and polycarbonate capacitors are film capacitors, too.

Here's an overview of the losses of different capacitor materials. Polycarbonate and polyester have higher losses than C0G, polypropylene and polystyrene have considerably lower losses than C0G.

The tempco of all of these film capacitor materials is worse than that for C0G.
 

grahamdavidmoore

Jun 23, 2014
9
Joined
Jun 23, 2014
Messages
9
I'll get one when I next order, I can see what difference it makes, just wanted to use the best I had at the moment, many thanks for your help
 

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
Messages
5,178
Looks like it a timing capacitor for some kind of linear ramp. Probably the best all rounder for the price is going to be a negative positive zero (NP0). Good all round over temperature and capacitance doesn't change much with applied voltage. But tolerance is generally +/-5%. Polystyrene is another good choice but can be damaged by soldering if your not careful.
Adam
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
That's a nice little circuit. A VCO for a synth, right?

If the designer recommends a C0G/NP0 that's what you should use. This one from Digikey looks good: http://www.digikey.com/product-detail/en/C412C222J5G5TA7200/399-4487-1-ND/818344

The initial tolerance is only ±5% but that can be compensated by adjustment. The temperature coefficient is what's important. AVX claim better than 30 ppm/°C for their C0G units and that's probably the best you'll find unless you want to spend big bucks.
 

grahamdavidmoore

Jun 23, 2014
9
Joined
Jun 23, 2014
Messages
9
Yes it is a vco so the stability is the main thing and vco's have always been very susceptible to temperature change
 
Top