Capacitor types - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: November 18, 2017, 02:37:00 pm
content: For non-precision beginner stuff is the value the most important part or does the type make a difference?I purchased two capacitor packs from bitsbox for ~£10 Thinking I was getting a sensible range, but I got lots of pF ceramics and lots of uF electrolytic and not a single nF. Of course everything I tried to do today wanted nF caps. Such as 1 and 10 nF bypass caps for ICs. Paralleling pF caps sounds like a faff.Bitsbox do a nF range but in polys. I can buy nF ceramics individually, I suppose I could get 1s, 10s, 100s which would cover most things.Does it really matter if the datasheet says use a 1nF ceramic when you have a 1nF poly?

author: w2aew
author_rank: Super Contributor
timestamp: November 18, 2017, 07:01:33 pm
content: For the most part, a poly cap will work as well as a ceramic, and often better (lower leakage, better tolerance, better voltage and temperature stability, etc.). You might be interested in my video on capacitor types and applications:

author: ocset
author_rank: Super Contributor
timestamp: November 18, 2017, 10:12:34 pm
content: depends on the use......electrolytics shoudl always be used at a voltage which is no more than the circuit voltage.Ceramics are kings of low inductance.Polys are usually big things.Ceramics have poor tolerance of not the right dielectricY5V ceramics have appalling tolerance.All ceramics have poor tolerance when used too near their rated voltage

author: wraper
author_rank: Unknown
timestamp: November 18, 2017, 10:18:26 pm
content: Quote from: treez on November 18, 2017, 10:12:34 pmNot all, only type 2 and 3 ceramics. Also it's highly capacitance/size dependent, say 4.7n 50V 0805 X7R won't drop much capacitance at rated voltage. C0G/NP0 capacitance is not voltage dependent.

author: wraper
author_rank: Unknown
timestamp: November 18, 2017, 10:22:25 pm
content: Quote from: paulca on November 18, 2017, 02:37:00 pmSuch capacitance usually is not used for bypassing unless it's some sort of high frequency stuff. 100nF is rule of thumb for general purpose bypassing.

author: TimFox
author_rank: Super Contributor
timestamp: November 19, 2017, 05:33:09 pm
content: For digital IC bypassing, a 10 nF X7R ceramic is a typical choice.For audio signal paths, use 10 nF polypropylene."Poly" could mean polyester (Mylar), polypropylene, or polystyrene, which differ.NP0/C0G ceramic (Type I) capacitors have good performance, but can be much larger than Type II capacitors, such as X7R.Type II and Type III capacitors (such as X7R, Y5U, and Z5U) have capacitance values that depend on the applied voltage, especially for the Type III capacitors, which are shown in good manufacturer's data sheets. For bypass use, this just means paying attention to the data sheet for the DC voltage applied, but for signal paths it is a source of non-linearity as the reactance varies with the voltage across the device.

author: wraper
author_rank: Unknown
timestamp: November 19, 2017, 05:46:58 pm
content: Quote from: TimFox on November 19, 2017, 05:33:09 pmOnly if it is high speed digital IC. And in such cases usually there will be something like 10nF in parallel with 100nF, not just 10nF by itself.

author: Gyro
author_rank: Super Contributor
timestamp: November 19, 2017, 06:31:28 pm
content: Quote from: treez on November 18, 2017, 10:12:34 pmHmmm, it would be pretty difficult to do otherwise!