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Why is it so hard to find ceramic capacitor kits that have a 3.3pF in it?

SparkyCal

Mar 11, 2020
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Why is it so hard to find ceramic capacitor kits that have a 3.3pF in it
 

Harald Kapp

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Because 3.3 pF are not very often required?
Also 3.3 pF can easily be created by a pair of adjacent traces or (better) a trace on a PCB above a ground plane.
If your circuit asks for a 3.3 pF capacitor, it is probably very sensitive to parasitic or stray capacitances from the PCB, the wiring, even from the components and will require very careful construction.
 

SparkyCal

Mar 11, 2020
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Because 3.3 pF are not very often required?
Also 3.3 pF can easily be created by a pair of adjacent traces or (better) a trace on a PCB above a ground plane.
If your circuit asks for a 3.3 pF capacitor, it is probably very sensitive to parasitic or stray capacitances from the PCB, the wiring, even from the components and will require very careful construction.
 

SparkyCal

Mar 11, 2020
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Thanks for the explanation. I found a kit that has a 3pf in it. I am hoping I can get away with that
 

Harald Kapp

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Considering that capacitors typically have +- 20 % tolerance (good ones +- 10 %, very good ones maybe +- 5 %) a 3 pF capacitor is as good as a 3.3 pF capacitor.

Have you ever wondered why resistors and capacitors have these crooked values as in the E-series? That is so that the individual values including tolerance bands cover the full range of possible values, which leads naturally to the logarithmic scale. And it also explains why the values get even more crooked when the tolerance improves).

These kits are imho useful to get you started. Once you build more and more circuits you will find that some values are required rather often, other rather seldom or almost never at all. By buying the kits again and again you will amass these rarely used components and you will not easily find a use for them.
I recommend that after you have set up a basic stock using these kits, you are better off buying the required componets according to the bill of materials. I also suggest you do not buy the exact numbe of components (unless they are expensive). It is always a good idea to have one or two spare parts just in case.
I'm sure you know by now how quickly an IC can be destroyed, a resistor can get burned etc. It as nothing to do with your capabilities - sh** happens ;)
 
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Audioguru

Sep 24, 2016
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His other post shows a theremin circuit with two 3.3pF capacitors in it to detect changes in the tiny capacitance of his hand's distance from an antenna. 3.3pF is almost nothing like the capacitance between your hand away from an antenna.
 

SparkyCal

Mar 11, 2020
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Thanks guys. i was able to order an inexpensive assortment of capacitors (less that $20), that includes 3pF capacitors. so hopefully that will work. I also read what you wrote in an old Radio Shack booklet on electronics, in which it talks about tolerances allowing for substitutions to an extent.
 
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