Capacitor types help please!!

[Seamus]

What are the best capacitors for a low noise setting?

What i mean is....out of Electrolyctic, Silver Mica, Metal Film, Disc, Tantalum, etc, which ones are the best to avoid noise?

[niftydog]

the one's with the lowest ESR:Capacitance ratio. (ESR = Equivalent Series Resistance)

You should first work out what values you need. Working out that silver micas have less noise than electrolytics doesn't help you when you need a 100­µF capacitor! For such large values, there's generally only one, maybe two choices; electros or tantalums.

Electrolytics come in so many varieties that I wouldn't be willing to say which has less noise. Regular cheap varieties would be more likely to cause noise. But, special low ESR caps might be better than even the best quality tantalums! I just don't know.

Having said all of that, capacitors do not contribute very much noise when compared to other parts of the circuit. Worry about low noise op amps and transistors first and use low value resistor wherever you can.

[Paul Perry (Frostwave)]

The noisiest component I ever saw in my life was an (accidentally) reverse-voltage 4.7 uF tantalum used as a coupling cap. The noise went right down to sub-sonic as well, the scope trace was staggering around drunkenly. Took a while to sort that one out :oops:

[Seamus]

Electrolyctic/Tantalum = bad. Silver Mica/Disk good? how do i find out the ESR?

[niftydog]

it will be specified in good component catalogues or in data available from the manufacturer. However, there are also "general" low ESR spec caps available for slightly more than the regular caps - the type used in switch mode power supplies are examples of these.

[Peter Snowberg]

Disc caps can be noisy thanks to the piezoelectric effect. It's a basic problem with many ceramics.

My favorite caps are....

for <1000pF - silver mica
for 1000pF to .47uF - metalized polyester (film caps)
for >.47uF - low ESR aluminum electrolytic