Different dielectric type.

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OK guys.
I will build my Very Low Noise and ultra low impedance Vref Generator just like JohnW did.
My question is quite simple.

The dielectric type of ceramic capacitors will have a major influence ?
It is like X7R vs NPO. The bad part is that the NPOs are SMD.

If i pick C3 as a tantalum, for the Voltage regulator it will be an improvement ?
 

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Hi,
Keep C3 ceramic.
Ceramic is good for high frequency.
NPO/COG have tighter tolerance: 5%.
X7R has 10% tolerance.

These dielectric have different temperature coefficient. You'll have to google this info, sorry.
According to the RS catalogue (p136), NPO is stable with temperature (0ppm/degree).
Serge
 
COG=NPO has not zero temperature coefficient it is 30ppm/degree

COG capaitors usually has tighter tolerance but you find them in values up to around 1nF.

From 1nF to 100nF usually X7R is used, it is a good dielectric but the temperature dependence is worse than COG (in your case does not matter at all).

From 100nF to 1uF X5R is normally used, the caracteristics are similar to X7R

There are also other dielectrics like Y5V or 5ZU with very bad temperature caracteristics and tolerances up to -80%/+20%. The only advantage of those dielectrics is that the allow high capacitance in a very small footprint. For example you can find capacitors up to 10uF in SMD 0603 case in Y5V.

In your case it is basically a decoupling capacitor, its value is not so important. Use a good quality ceramic cap, don't care too much to the dielectric
 

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